diff --git a/include/openmc/mesh.h b/include/openmc/mesh.h
index f4a6dcc33e..eecb06a204 100644
--- a/include/openmc/mesh.h
+++ b/include/openmc/mesh.h
@@ -41,6 +41,8 @@ namespace openmc {
 // Global variables
 //==============================================================================
 
+extern "C" const bool libmesh_enabled;
+
 class Mesh;
 
 namespace model {
@@ -277,17 +279,12 @@ public:
 class UnstructuredMesh : public Mesh {
 
 public:
-  // constructors
+  // Constructors
   UnstructuredMesh() {};
   UnstructuredMesh(pugi::xml_node node);
   UnstructuredMesh(const std::string& filename);
 
-  std::string bin_label(int bin) const override;
-
-  //! Write mesh data to an HDF5 group.
-  //
-  //! \param[in] group HDF5 group
-  void to_hdf5(hid_t group) const;
+  // Methods
 
   //! Add a variable to the mesh instance
   virtual void add_score(const std::string& var_name) = 0;
@@ -297,14 +294,31 @@ public:
                               std::vector<double> values,
                               std::vector<double> std_dev) = 0;
 
+  //! Write the unstructured mesh to file
+  //
+  //
+  //! \param[in] filename Name of the file to write
   virtual void write(std::string filename) const = 0;
 
+  //! Retrieve a centroid for the mesh cell
+  //
+  //! \param[in] bin Bin to return the centroid for
+  //! \return The centroid of the bin
   virtual Position centroid(int bin) const = 0;
 
+  //! Get the volume of a mesh bin
+  //
+  //! \param[in] bin Bin to return the volume for
+  //! \return The volume of the bin
   virtual double volume(int bin) const = 0;
 
+  //! Get the library used for this unstructured mesh
   virtual std::string library() const = 0;
 
+  std::string bin_label(int bin) const override;
+
+  void to_hdf5(hid_t group) const override;
+
   // Data members
   std::string filename_; //!< Path to unstructured mesh file
 };
@@ -331,27 +345,18 @@ public:
   //
   //! \param[in] p Particle to check
   //! \param[out] bins Surface bins that were crossed
-  void surface_bins_crossed(const Particle& p, std::vector<int>& bins) const;
+  void surface_bins_crossed(const Particle* p, std::vector<int>& bins) const;
 
-  //! Get bin at a given position.
-  //
-  //! \param[in] r Position to get bin for
-  //! \return Mesh bin
   int get_bin(Position r) const;
 
-  std::string library() const override;
-
   int n_bins() const override;
 
   int n_surface_bins() const override;
 
-  //! Retrieve a centroid for the mesh cell
-  //
-  // \param[in] bin Bin to return the volume for
-  // \return The centroid of the element
-  Position centroid(int bin) const override;
+  std::pair<std::vector<double>, std::vector<double>>
+  plot(Position plot_ll, Position plot_ur) const override;
 
-  double volume(int bin) const override;
+  std::string library() const override;
 
   //! Add a score to the mesh instance
   void add_score(const std::string& score);
@@ -372,7 +377,9 @@ public:
   //! Write the mesh with any current tally data
   void write(std::string base_filename) const;
 
-  bool intersects(Position& r0, Position r1, int* ijk);
+  Position centroid(int bin) const override;
+
+  double volume(int bin) const override;
 
 private:
 
@@ -468,7 +475,7 @@ private:
   std::pair<moab::Tag, moab::Tag>
   get_score_tags(std::string score) const;
 
-  // data members
+  // Data members
   moab::Range ehs_; //!< Range of tetrahedra EntityHandle's in the mesh
   moab::EntityHandle tetset_; //!< EntitySet containing all tetrahedra
   moab::EntityHandle kdtree_root_; //!< Root of the MOAB KDTree
@@ -490,40 +497,35 @@ public:
   LibMesh(const std::string& filename);
 
   // Methods
-
-  // standard mesh functions
   void bins_crossed(const Particle* p,
                     std::vector<int>& bins,
                     std::vector<double>& lengths) const override;
 
-  int get_bin(Position r) const override;
+  void surface_bins_crossed(const Particle* p, std::vector<int>& bins) const override;
 
-  std::string library() const override;
+  int get_bin(Position r) const override;
 
   int n_bins() const override;
 
   int n_surface_bins() const override;
 
-  void surface_bins_crossed(const Particle* p,
-                             std::vector<int>& bins) const override;
-
   std::pair<std::vector<double>, std::vector<double>> plot(Position plot_ll,
                                                            Position plot_ur) const override;
 
-  void write(std::string filename) const override;
-
-  //! Add a variable to the libmesh mesh instance
   void add_score(const std::string& var_name) override;
 
-  //! Set the value of a bin for a variable on the libmesh mesh instance
   void set_score_data(const std::string& var_name,
                       std::vector<double> values,
                       std::vector<double> std_dev) override;
 
+  void write(std::string filename) const override;
+
   Position centroid(int bin) const override;
 
   double volume(int bin) const override;
 
+  std::string library() const override;
+
 private:
 
   //! Setup method for the mesh. Builds data structures,
@@ -536,43 +538,14 @@ private:
   //! Translate an element pointer to a bin value
   int get_bin_from_element(const libMesh::Elem* elem) const;
 
-  //! Check whether if a point moving in a given direction
-  //! is inside the element
-  //
-  //! \param[in] r In: point to be checked
-  //! \param[in] u In: direction (this is arbitrary, any normalized direction will do)
-  //! \param[in] e In: libmesh element in question
-  //! \return whether or not the point is in the tet
-  bool inside_tet(const libMesh::Point& r,
-                  const libMesh::Point& u,
-                  const libMesh::Elem* e) const;
-
-  //! Check if a point moving in a given direction
-  //! is inside the element
-  //
-  //! \param[in] r In: point to be checked
-  //! \param[in] u In: direction (this is arbitrary, any normalized direction will do)
-  //! \param[in] e In: libmesh element in question
-  //! \return whether or not the point is in the tet
-  bool inside_tet(const libMesh::Point& r,
-                  const libMesh::Point& u,
-                  std::unique_ptr<libMesh::Elem> e) const;
-
-  double first(const libMesh::Node& a,
-               const libMesh::Node& b) const;
-
   // Data members
-
-private:
   std::unique_ptr<libMesh::Mesh> m_; //!< pointer to the libmesh mesh instance
   std::vector<std::unique_ptr<libMesh::PointLocatorBase>> point_locators_; //!< pointers to locators for each thread
   std::unique_ptr<libMesh::EquationSystems> equation_systems_; //!< pointer to the equation systems of the mesh (for result output)
   std::map<std::string, unsigned int> variable_map_; //!< mapping of variable names (scores) to their numbers on the mesh
   libMesh::BoundingBox bbox_; //!< bounding box of the mesh
-  libMesh::Sphere bsphere_; //<! bounding sphere of the mesh
   std::string eq_system_name_; //!< name of the equation system holding OpenMC results
   libMesh::Elem* first_element_; //!< pointer to the first element in the mesh (maybe should be a key?)
-  std::set<libMesh::Elem*> boundary_elements_; //<! all boundary elements in the mesh
 };
 #endif
 
diff --git a/openmc/lib/__init__.py b/openmc/lib/__init__.py
index 8a2d3cf7ba..9a72403ff4 100644
--- a/openmc/lib/__init__.py
+++ b/openmc/lib/__init__.py
@@ -45,6 +45,9 @@ def _dagmc_enabled():
 def _coord_levels():
     return c_int.in_dll(_dll, "n_coord_levels").value
 
+def _libmesh_enabled():
+    return c_bool.in_dll(_dll, "libmesh_enabled").value
+
 from .error import *
 from .core import *
 from .nuclide import *
diff --git a/openmc/mesh.py b/openmc/mesh.py
index 2559a0f56d..4d65db2a96 100644
--- a/openmc/mesh.py
+++ b/openmc/mesh.py
@@ -632,7 +632,7 @@ class UnstructuredMesh(MeshBase):
         self.filename = filename
         self._volumes = None
         self._centroids = None
-        self._mesh_lib = 'moab'
+        self._library = 'moab'
 
     @property
     def filename(self):
@@ -644,13 +644,13 @@ class UnstructuredMesh(MeshBase):
         self._filename = filename
 
     @property
-    def mesh_lib(self):
+    def library(self):
         return self._mesh_lib
 
-    @mesh_lib.setter
-    def mesh_lib(self, mesh_lib):
+    @library.setter
+    def library(self, mesh_lib):
         cv.check_value('mesh_lib', mesh_lib, ('moab', 'libmesh'))
-        self._mesh_lib = mesh_lib
+        self._library = mesh_lib
 
     @property
     def size(self):
@@ -811,7 +811,7 @@ class UnstructuredMesh(MeshBase):
         element.set("id", str(self._id))
         element.set("type", "unstructured")
         subelement = ET.SubElement(element, "filename")
-        element.set("library", self._mesh_lib)
+        element.set("library", self._library)
         subelement.text = self.filename
 
         return element
diff --git a/src/mesh.cpp b/src/mesh.cpp
index 47f9a1d611..a967828fe4 100644
--- a/src/mesh.cpp
+++ b/src/mesh.cpp
@@ -39,6 +39,13 @@ namespace openmc {
 // Global variables
 //==============================================================================
 
+#ifdef LIBMESH
+const bool libmesh_enabled = true;
+#else
+const bool libmesh_enabled = false;
+#endif
+
+
 namespace model {
 
 std::unordered_map<int32_t, int32_t> mesh_map;
@@ -2205,25 +2212,10 @@ void LibMesh::initialize() {
     point_locators_[i]->enable_out_of_mesh_mode();
   }
 
-  // will need mesh neighbors to walk the mesh
-  m_->find_neighbors();
-
   first_element_ = *m_->elements_begin();
 
   // bounding box for the mesh
   bbox_ = libMesh::MeshTools::create_bounding_box(*m_);
-  bsphere_ = libMesh::MeshTools::bounding_sphere(*m_);
-
-  // determine boundary elements and create bounding box
-  for (int i = 0; i < m_->n_elem(); i++) {
-    auto e = m_->elem_ptr(i);
-
-    for (int k = 0; k < e->n_neighbors(); k++) {
-      if (!e->neighbor_ptr(k)) {
-        boundary_elements_.insert(e);
-      }
-    }
-  }
 }
 
 int LibMesh::n_bins() const {
@@ -2243,15 +2235,6 @@ LibMesh::surface_bins_crossed(const Particle* p,
   throw std::runtime_error{"Unstructured mesh surface tallies are not implemented."};
 }
 
-std::pair<std::vector<double>, std::vector<double>>
-LibMesh::plot(Position plot_ll,
-              Position plot_ur) const { return {}; }
-
-const libMesh::Elem*
-LibMesh::get_element_from_bin(int bin) const {
-  return m_->elem_ptr(bin);
-}
-
 void
 LibMesh::add_score(const std::string& var_name) {
   // check if this is a new varaible
@@ -2309,7 +2292,7 @@ LibMesh::set_score_data(const std::string& var_name,
 void LibMesh::write(std::string filename) const {
   libMesh::ExodusII_IO exo(*m_);
   std::set<std::string> systems_out = {eq_system_name_};
-  exo.write_discontinuous_exodusII(filename, *equation_systems_, &systems_out);
+  exo.write_discontinuous_exodusII(filename + ".e", *equation_systems_, &systems_out);
 }
 
 void
@@ -2328,11 +2311,10 @@ LibMesh::get_bin(Position r) const
   libMesh::Point p(r.x, r.y, r.z);
 
   // quick rejection check
-  //  if (bsphere_.above_surface(p) || !bbox_.contains_point(p)) { return -1; }
   if (!bbox_.contains_point(p)) { return -1; }
-  int thread = omp_get_thread_num();
-  auto e = (*point_locators_[thread])(p);
 
+  int thread = omp_get_thread_num();
+  auto e = (*point_locators_[thread])(p, false);
   if (!e) {
     return -1;
   } else {
@@ -2343,29 +2325,19 @@ LibMesh::get_bin(Position r) const
 int
 LibMesh::get_bin_from_element(const libMesh::Elem* elem) const {
   int bin =  elem->id() - first_element_->id();
-  if (bin >= n_bins()) {
-    std::stringstream s;
-    s << "Invalid bin: " << bin;
-    fatal_error(s);
+  if (bin >= n_bins() || bin < 0) {
+    fatal_error(fmt::format("Invalid bin: {}", bin));
   }
   return bin;
 }
 
-bool
-LibMesh::inside_tet(const libMesh::Point& r,
-                    const libMesh::Point& u,
-                    std::unique_ptr<libMesh::Elem> e) const
-{
-  return inside_tet(r, u, e.get());
-}
+std::pair<std::vector<double>, std::vector<double>>
+LibMesh::plot(Position plot_ll,
+              Position plot_ur) const { return {}; }
 
-
-bool
-LibMesh::inside_tet(const libMesh::Point& r,
-                    const libMesh::Point& u,
-                    const libMesh::Elem* e) const
-{
-  return e->contains_point(r, FP_COINCIDENT);
+const libMesh::Elem*
+LibMesh::get_element_from_bin(int bin) const {
+  return m_->elem_ptr(bin);
 }
 
 double LibMesh::volume(int bin) const { return m_->elem_ref(bin).volume(); }
diff --git a/tests/regression_tests/unstructured_mesh/inputs_true0.dat b/tests/regression_tests/unstructured_mesh/inputs_true0.dat
index 897d79917f..916b77f0fb 100644
--- a/tests/regression_tests/unstructured_mesh/inputs_true0.dat
+++ b/tests/regression_tests/unstructured_mesh/inputs_true0.dat
@@ -70,8 +70,8 @@
     <lower_left>-10.0 -10.0 -10.0</lower_left>
     <upper_right>10.0 10.0 10.0</upper_right>
   </mesh>
-  <mesh id="2" library="moab" type="unstructured">
-    <filename>test_mesh_tets_w_holes.h5m</filename>
+  <mesh id="2" library="libmesh" type="unstructured">
+    <filename>test_mesh_tets_w_holes.exo</filename>
   </mesh>
   <filter id="1" type="mesh">
     <bins>1</bins>
diff --git a/tests/regression_tests/unstructured_mesh/inputs_true1.dat b/tests/regression_tests/unstructured_mesh/inputs_true1.dat
index 5461b8df1f..a8633ab75d 100644
--- a/tests/regression_tests/unstructured_mesh/inputs_true1.dat
+++ b/tests/regression_tests/unstructured_mesh/inputs_true1.dat
@@ -70,8 +70,8 @@
     <lower_left>-10.0 -10.0 -10.0</lower_left>
     <upper_right>10.0 10.0 10.0</upper_right>
   </mesh>
-  <mesh id="4" library="moab" type="unstructured">
-    <filename>test_mesh_tets.h5m</filename>
+  <mesh id="4" library="libmesh" type="unstructured">
+    <filename>test_mesh_tets.exo</filename>
   </mesh>
   <filter id="3" type="mesh">
     <bins>3</bins>
diff --git a/tests/regression_tests/unstructured_mesh/inputs_true10.dat b/tests/regression_tests/unstructured_mesh/inputs_true10.dat
new file mode 100644
index 0000000000..cb5a96a0ce
--- /dev/null
+++ b/tests/regression_tests/unstructured_mesh/inputs_true10.dat
@@ -0,0 +1,92 @@
+<?xml version='1.0' encoding='utf-8'?>
+<geometry>
+  <cell id="19" material="19" name="fuel" region="109 -110 111 -112 113 -114" universe="7" />
+  <cell id="20" material="20" name="clad" region="(-109 | 110 | -111 | 112 | -113 | 114) (115 -116 117 -118 119 -120)" universe="7" />
+  <cell id="21" material="21" name="water" region="(-115 | 116 | -117 | 118 | -119 | 120) (121 -122 123 -124 125 -126)" universe="7" />
+  <surface coeffs="-5.0" id="109" name="minimum x" type="x-plane" />
+  <surface coeffs="5.0" id="110" name="maximum x" type="x-plane" />
+  <surface coeffs="-5.0" id="111" name="minimum y" type="y-plane" />
+  <surface coeffs="5.0" id="112" name="maximum y" type="y-plane" />
+  <surface coeffs="-5.0" id="113" name="minimum z" type="z-plane" />
+  <surface coeffs="5.0" id="114" name="maximum z" type="z-plane" />
+  <surface coeffs="-6.0" id="115" name="minimum x" type="x-plane" />
+  <surface coeffs="6.0" id="116" name="maximum x" type="x-plane" />
+  <surface coeffs="-6.0" id="117" name="minimum y" type="y-plane" />
+  <surface coeffs="6.0" id="118" name="maximum y" type="y-plane" />
+  <surface coeffs="-6.0" id="119" name="minimum z" type="z-plane" />
+  <surface coeffs="6.0" id="120" name="maximum z" type="z-plane" />
+  <surface boundary="vacuum" coeffs="-10" id="121" name="minimum x" type="x-plane" />
+  <surface boundary="vacuum" coeffs="10" id="122" name="maximum x" type="x-plane" />
+  <surface boundary="vacuum" coeffs="-10" id="123" name="minimum y" type="y-plane" />
+  <surface boundary="vacuum" coeffs="10" id="124" name="maximum y" type="y-plane" />
+  <surface boundary="vacuum" coeffs="-10" id="125" name="minimum z" type="z-plane" />
+  <surface boundary="vacuum" coeffs="10" id="126" name="maximum z" type="z-plane" />
+</geometry>
+<?xml version='1.0' encoding='utf-8'?>
+<materials>
+  <material depletable="true" id="19" name="fuel">
+    <density units="g/cc" value="4.5" />
+    <nuclide ao="1.0" name="U235" />
+  </material>
+  <material id="20" name="zircaloy">
+    <density units="g/cc" value="5.77" />
+    <nuclide ao="0.5145" name="Zr90" />
+    <nuclide ao="0.1122" name="Zr91" />
+    <nuclide ao="0.1715" name="Zr92" />
+    <nuclide ao="0.1738" name="Zr94" />
+    <nuclide ao="0.028" name="Zr96" />
+  </material>
+  <material id="21" name="water">
+    <density units="atom/b-cm" value="0.07416" />
+    <nuclide ao="2.0" name="H1" />
+    <nuclide ao="1.0" name="O16" />
+  </material>
+</materials>
+<?xml version='1.0' encoding='utf-8'?>
+<settings>
+  <run_mode>fixed source</run_mode>
+  <particles>100</particles>
+  <batches>10</batches>
+  <source strength="1.0">
+    <space origin="0.0 0.0 0.0" type="spherical">
+      <r parameters="0.0 0.0" type="uniform" />
+      <theta type="discrete">
+        <parameters>0.0 1.0</parameters>
+      </theta>
+      <phi type="discrete">
+        <parameters>0.0 1.0</parameters>
+      </phi>
+    </space>
+    <angle reference_uvw="-1.0 0.0 0.0" type="monodirectional" />
+    <energy type="discrete">
+      <parameters>15000000.0 1.0</parameters>
+    </energy>
+  </source>
+</settings>
+<?xml version='1.0' encoding='utf-8'?>
+<tallies>
+  <mesh id="13">
+    <dimension>10 10 10</dimension>
+    <lower_left>-10.0 -10.0 -10.0</lower_left>
+    <upper_right>10.0 10.0 10.0</upper_right>
+  </mesh>
+  <mesh id="14" library="moab" type="unstructured">
+    <filename>test_mesh_tets_w_holes.exo</filename>
+  </mesh>
+  <filter id="13" type="mesh">
+    <bins>13</bins>
+  </filter>
+  <filter id="14" type="mesh">
+    <bins>14</bins>
+  </filter>
+  <tally id="13" name="regular mesh tally">
+    <filters>13</filters>
+    <scores>flux</scores>
+    <estimator>collision</estimator>
+  </tally>
+  <tally id="14" name="unstructured mesh tally">
+    <filters>14</filters>
+    <scores>flux</scores>
+    <estimator>collision</estimator>
+  </tally>
+</tallies>
diff --git a/tests/regression_tests/unstructured_mesh/inputs_true11.dat b/tests/regression_tests/unstructured_mesh/inputs_true11.dat
new file mode 100644
index 0000000000..f721422f1d
--- /dev/null
+++ b/tests/regression_tests/unstructured_mesh/inputs_true11.dat
@@ -0,0 +1,92 @@
+<?xml version='1.0' encoding='utf-8'?>
+<geometry>
+  <cell id="22" material="22" name="fuel" region="127 -128 129 -130 131 -132" universe="8" />
+  <cell id="23" material="23" name="clad" region="(-127 | 128 | -129 | 130 | -131 | 132) (133 -134 135 -136 137 -138)" universe="8" />
+  <cell id="24" material="24" name="water" region="(-133 | 134 | -135 | 136 | -137 | 138) (139 -140 141 -142 143 -144)" universe="8" />
+  <surface coeffs="-5.0" id="127" name="minimum x" type="x-plane" />
+  <surface coeffs="5.0" id="128" name="maximum x" type="x-plane" />
+  <surface coeffs="-5.0" id="129" name="minimum y" type="y-plane" />
+  <surface coeffs="5.0" id="130" name="maximum y" type="y-plane" />
+  <surface coeffs="-5.0" id="131" name="minimum z" type="z-plane" />
+  <surface coeffs="5.0" id="132" name="maximum z" type="z-plane" />
+  <surface coeffs="-6.0" id="133" name="minimum x" type="x-plane" />
+  <surface coeffs="6.0" id="134" name="maximum x" type="x-plane" />
+  <surface coeffs="-6.0" id="135" name="minimum y" type="y-plane" />
+  <surface coeffs="6.0" id="136" name="maximum y" type="y-plane" />
+  <surface coeffs="-6.0" id="137" name="minimum z" type="z-plane" />
+  <surface coeffs="6.0" id="138" name="maximum z" type="z-plane" />
+  <surface boundary="vacuum" coeffs="-10" id="139" name="minimum x" type="x-plane" />
+  <surface boundary="vacuum" coeffs="10" id="140" name="maximum x" type="x-plane" />
+  <surface boundary="vacuum" coeffs="-10" id="141" name="minimum y" type="y-plane" />
+  <surface boundary="vacuum" coeffs="10" id="142" name="maximum y" type="y-plane" />
+  <surface boundary="vacuum" coeffs="-10" id="143" name="minimum z" type="z-plane" />
+  <surface boundary="vacuum" coeffs="10" id="144" name="maximum z" type="z-plane" />
+</geometry>
+<?xml version='1.0' encoding='utf-8'?>
+<materials>
+  <material depletable="true" id="22" name="fuel">
+    <density units="g/cc" value="4.5" />
+    <nuclide ao="1.0" name="U235" />
+  </material>
+  <material id="23" name="zircaloy">
+    <density units="g/cc" value="5.77" />
+    <nuclide ao="0.5145" name="Zr90" />
+    <nuclide ao="0.1122" name="Zr91" />
+    <nuclide ao="0.1715" name="Zr92" />
+    <nuclide ao="0.1738" name="Zr94" />
+    <nuclide ao="0.028" name="Zr96" />
+  </material>
+  <material id="24" name="water">
+    <density units="atom/b-cm" value="0.07416" />
+    <nuclide ao="2.0" name="H1" />
+    <nuclide ao="1.0" name="O16" />
+  </material>
+</materials>
+<?xml version='1.0' encoding='utf-8'?>
+<settings>
+  <run_mode>fixed source</run_mode>
+  <particles>100</particles>
+  <batches>10</batches>
+  <source strength="1.0">
+    <space origin="0.0 0.0 0.0" type="spherical">
+      <r parameters="0.0 0.0" type="uniform" />
+      <theta type="discrete">
+        <parameters>0.0 1.0</parameters>
+      </theta>
+      <phi type="discrete">
+        <parameters>0.0 1.0</parameters>
+      </phi>
+    </space>
+    <angle reference_uvw="-1.0 0.0 0.0" type="monodirectional" />
+    <energy type="discrete">
+      <parameters>15000000.0 1.0</parameters>
+    </energy>
+  </source>
+</settings>
+<?xml version='1.0' encoding='utf-8'?>
+<tallies>
+  <mesh id="15">
+    <dimension>10 10 10</dimension>
+    <lower_left>-10.0 -10.0 -10.0</lower_left>
+    <upper_right>10.0 10.0 10.0</upper_right>
+  </mesh>
+  <mesh id="16" library="moab" type="unstructured">
+    <filename>test_mesh_tets.exo</filename>
+  </mesh>
+  <filter id="15" type="mesh">
+    <bins>15</bins>
+  </filter>
+  <filter id="16" type="mesh">
+    <bins>16</bins>
+  </filter>
+  <tally id="15" name="regular mesh tally">
+    <filters>15</filters>
+    <scores>flux</scores>
+    <estimator>collision</estimator>
+  </tally>
+  <tally id="16" name="unstructured mesh tally">
+    <filters>16</filters>
+    <scores>flux</scores>
+    <estimator>collision</estimator>
+  </tally>
+</tallies>
diff --git a/tests/regression_tests/unstructured_mesh/inputs_true12.dat b/tests/regression_tests/unstructured_mesh/inputs_true12.dat
new file mode 100644
index 0000000000..f29b4ca6af
--- /dev/null
+++ b/tests/regression_tests/unstructured_mesh/inputs_true12.dat
@@ -0,0 +1,92 @@
+<?xml version='1.0' encoding='utf-8'?>
+<geometry>
+  <cell id="25" material="25" name="fuel" region="145 -146 147 -148 149 -150" universe="9" />
+  <cell id="26" material="26" name="clad" region="(-145 | 146 | -147 | 148 | -149 | 150) (151 -152 153 -154 155 -156)" universe="9" />
+  <cell id="27" material="27" name="water" region="(-151 | 152 | -153 | 154 | -155 | 156) (157 -158 159 -160 161 -162)" universe="9" />
+  <surface coeffs="-5.0" id="145" name="minimum x" type="x-plane" />
+  <surface coeffs="5.0" id="146" name="maximum x" type="x-plane" />
+  <surface coeffs="-5.0" id="147" name="minimum y" type="y-plane" />
+  <surface coeffs="5.0" id="148" name="maximum y" type="y-plane" />
+  <surface coeffs="-5.0" id="149" name="minimum z" type="z-plane" />
+  <surface coeffs="5.0" id="150" name="maximum z" type="z-plane" />
+  <surface coeffs="-6.0" id="151" name="minimum x" type="x-plane" />
+  <surface coeffs="6.0" id="152" name="maximum x" type="x-plane" />
+  <surface coeffs="-6.0" id="153" name="minimum y" type="y-plane" />
+  <surface coeffs="6.0" id="154" name="maximum y" type="y-plane" />
+  <surface coeffs="-6.0" id="155" name="minimum z" type="z-plane" />
+  <surface coeffs="6.0" id="156" name="maximum z" type="z-plane" />
+  <surface boundary="vacuum" coeffs="-15" id="157" name="minimum x" type="x-plane" />
+  <surface boundary="vacuum" coeffs="15" id="158" name="maximum x" type="x-plane" />
+  <surface boundary="vacuum" coeffs="-15" id="159" name="minimum y" type="y-plane" />
+  <surface boundary="vacuum" coeffs="15" id="160" name="maximum y" type="y-plane" />
+  <surface boundary="vacuum" coeffs="-15" id="161" name="minimum z" type="z-plane" />
+  <surface boundary="vacuum" coeffs="15" id="162" name="maximum z" type="z-plane" />
+</geometry>
+<?xml version='1.0' encoding='utf-8'?>
+<materials>
+  <material depletable="true" id="25" name="fuel">
+    <density units="g/cc" value="4.5" />
+    <nuclide ao="1.0" name="U235" />
+  </material>
+  <material id="26" name="zircaloy">
+    <density units="g/cc" value="5.77" />
+    <nuclide ao="0.5145" name="Zr90" />
+    <nuclide ao="0.1122" name="Zr91" />
+    <nuclide ao="0.1715" name="Zr92" />
+    <nuclide ao="0.1738" name="Zr94" />
+    <nuclide ao="0.028" name="Zr96" />
+  </material>
+  <material id="27" name="water">
+    <density units="atom/b-cm" value="0.07416" />
+    <nuclide ao="2.0" name="H1" />
+    <nuclide ao="1.0" name="O16" />
+  </material>
+</materials>
+<?xml version='1.0' encoding='utf-8'?>
+<settings>
+  <run_mode>fixed source</run_mode>
+  <particles>100</particles>
+  <batches>10</batches>
+  <source strength="1.0">
+    <space origin="0.0 0.0 0.0" type="spherical">
+      <r parameters="0.0 0.0" type="uniform" />
+      <theta type="discrete">
+        <parameters>0.0 1.0</parameters>
+      </theta>
+      <phi type="discrete">
+        <parameters>0.0 1.0</parameters>
+      </phi>
+    </space>
+    <angle reference_uvw="-1.0 0.0 0.0" type="monodirectional" />
+    <energy type="discrete">
+      <parameters>15000000.0 1.0</parameters>
+    </energy>
+  </source>
+</settings>
+<?xml version='1.0' encoding='utf-8'?>
+<tallies>
+  <mesh id="17">
+    <dimension>10 10 10</dimension>
+    <lower_left>-10.0 -10.0 -10.0</lower_left>
+    <upper_right>10.0 10.0 10.0</upper_right>
+  </mesh>
+  <mesh id="18" library="moab" type="unstructured">
+    <filename>test_mesh_tets_w_holes.exo</filename>
+  </mesh>
+  <filter id="17" type="mesh">
+    <bins>17</bins>
+  </filter>
+  <filter id="18" type="mesh">
+    <bins>18</bins>
+  </filter>
+  <tally id="17" name="regular mesh tally">
+    <filters>17</filters>
+    <scores>flux</scores>
+    <estimator>tracklength</estimator>
+  </tally>
+  <tally id="18" name="unstructured mesh tally">
+    <filters>18</filters>
+    <scores>flux</scores>
+    <estimator>tracklength</estimator>
+  </tally>
+</tallies>
diff --git a/tests/regression_tests/unstructured_mesh/inputs_true13.dat b/tests/regression_tests/unstructured_mesh/inputs_true13.dat
new file mode 100644
index 0000000000..e2337e1ae0
--- /dev/null
+++ b/tests/regression_tests/unstructured_mesh/inputs_true13.dat
@@ -0,0 +1,92 @@
+<?xml version='1.0' encoding='utf-8'?>
+<geometry>
+  <cell id="28" material="28" name="fuel" region="163 -164 165 -166 167 -168" universe="10" />
+  <cell id="29" material="29" name="clad" region="(-163 | 164 | -165 | 166 | -167 | 168) (169 -170 171 -172 173 -174)" universe="10" />
+  <cell id="30" material="30" name="water" region="(-169 | 170 | -171 | 172 | -173 | 174) (175 -176 177 -178 179 -180)" universe="10" />
+  <surface coeffs="-5.0" id="163" name="minimum x" type="x-plane" />
+  <surface coeffs="5.0" id="164" name="maximum x" type="x-plane" />
+  <surface coeffs="-5.0" id="165" name="minimum y" type="y-plane" />
+  <surface coeffs="5.0" id="166" name="maximum y" type="y-plane" />
+  <surface coeffs="-5.0" id="167" name="minimum z" type="z-plane" />
+  <surface coeffs="5.0" id="168" name="maximum z" type="z-plane" />
+  <surface coeffs="-6.0" id="169" name="minimum x" type="x-plane" />
+  <surface coeffs="6.0" id="170" name="maximum x" type="x-plane" />
+  <surface coeffs="-6.0" id="171" name="minimum y" type="y-plane" />
+  <surface coeffs="6.0" id="172" name="maximum y" type="y-plane" />
+  <surface coeffs="-6.0" id="173" name="minimum z" type="z-plane" />
+  <surface coeffs="6.0" id="174" name="maximum z" type="z-plane" />
+  <surface boundary="vacuum" coeffs="-15" id="175" name="minimum x" type="x-plane" />
+  <surface boundary="vacuum" coeffs="15" id="176" name="maximum x" type="x-plane" />
+  <surface boundary="vacuum" coeffs="-15" id="177" name="minimum y" type="y-plane" />
+  <surface boundary="vacuum" coeffs="15" id="178" name="maximum y" type="y-plane" />
+  <surface boundary="vacuum" coeffs="-15" id="179" name="minimum z" type="z-plane" />
+  <surface boundary="vacuum" coeffs="15" id="180" name="maximum z" type="z-plane" />
+</geometry>
+<?xml version='1.0' encoding='utf-8'?>
+<materials>
+  <material depletable="true" id="28" name="fuel">
+    <density units="g/cc" value="4.5" />
+    <nuclide ao="1.0" name="U235" />
+  </material>
+  <material id="29" name="zircaloy">
+    <density units="g/cc" value="5.77" />
+    <nuclide ao="0.5145" name="Zr90" />
+    <nuclide ao="0.1122" name="Zr91" />
+    <nuclide ao="0.1715" name="Zr92" />
+    <nuclide ao="0.1738" name="Zr94" />
+    <nuclide ao="0.028" name="Zr96" />
+  </material>
+  <material id="30" name="water">
+    <density units="atom/b-cm" value="0.07416" />
+    <nuclide ao="2.0" name="H1" />
+    <nuclide ao="1.0" name="O16" />
+  </material>
+</materials>
+<?xml version='1.0' encoding='utf-8'?>
+<settings>
+  <run_mode>fixed source</run_mode>
+  <particles>100</particles>
+  <batches>10</batches>
+  <source strength="1.0">
+    <space origin="0.0 0.0 0.0" type="spherical">
+      <r parameters="0.0 0.0" type="uniform" />
+      <theta type="discrete">
+        <parameters>0.0 1.0</parameters>
+      </theta>
+      <phi type="discrete">
+        <parameters>0.0 1.0</parameters>
+      </phi>
+    </space>
+    <angle reference_uvw="-1.0 0.0 0.0" type="monodirectional" />
+    <energy type="discrete">
+      <parameters>15000000.0 1.0</parameters>
+    </energy>
+  </source>
+</settings>
+<?xml version='1.0' encoding='utf-8'?>
+<tallies>
+  <mesh id="19">
+    <dimension>10 10 10</dimension>
+    <lower_left>-10.0 -10.0 -10.0</lower_left>
+    <upper_right>10.0 10.0 10.0</upper_right>
+  </mesh>
+  <mesh id="20" library="moab" type="unstructured">
+    <filename>test_mesh_tets.exo</filename>
+  </mesh>
+  <filter id="19" type="mesh">
+    <bins>19</bins>
+  </filter>
+  <filter id="20" type="mesh">
+    <bins>20</bins>
+  </filter>
+  <tally id="19" name="regular mesh tally">
+    <filters>19</filters>
+    <scores>flux</scores>
+    <estimator>tracklength</estimator>
+  </tally>
+  <tally id="20" name="unstructured mesh tally">
+    <filters>20</filters>
+    <scores>flux</scores>
+    <estimator>tracklength</estimator>
+  </tally>
+</tallies>
diff --git a/tests/regression_tests/unstructured_mesh/inputs_true14.dat b/tests/regression_tests/unstructured_mesh/inputs_true14.dat
new file mode 100644
index 0000000000..b8f90877fa
--- /dev/null
+++ b/tests/regression_tests/unstructured_mesh/inputs_true14.dat
@@ -0,0 +1,92 @@
+<?xml version='1.0' encoding='utf-8'?>
+<geometry>
+  <cell id="31" material="31" name="fuel" region="181 -182 183 -184 185 -186" universe="11" />
+  <cell id="32" material="32" name="clad" region="(-181 | 182 | -183 | 184 | -185 | 186) (187 -188 189 -190 191 -192)" universe="11" />
+  <cell id="33" material="33" name="water" region="(-187 | 188 | -189 | 190 | -191 | 192) (193 -194 195 -196 197 -198)" universe="11" />
+  <surface coeffs="-5.0" id="181" name="minimum x" type="x-plane" />
+  <surface coeffs="5.0" id="182" name="maximum x" type="x-plane" />
+  <surface coeffs="-5.0" id="183" name="minimum y" type="y-plane" />
+  <surface coeffs="5.0" id="184" name="maximum y" type="y-plane" />
+  <surface coeffs="-5.0" id="185" name="minimum z" type="z-plane" />
+  <surface coeffs="5.0" id="186" name="maximum z" type="z-plane" />
+  <surface coeffs="-6.0" id="187" name="minimum x" type="x-plane" />
+  <surface coeffs="6.0" id="188" name="maximum x" type="x-plane" />
+  <surface coeffs="-6.0" id="189" name="minimum y" type="y-plane" />
+  <surface coeffs="6.0" id="190" name="maximum y" type="y-plane" />
+  <surface coeffs="-6.0" id="191" name="minimum z" type="z-plane" />
+  <surface coeffs="6.0" id="192" name="maximum z" type="z-plane" />
+  <surface boundary="vacuum" coeffs="-10" id="193" name="minimum x" type="x-plane" />
+  <surface boundary="vacuum" coeffs="10" id="194" name="maximum x" type="x-plane" />
+  <surface boundary="vacuum" coeffs="-10" id="195" name="minimum y" type="y-plane" />
+  <surface boundary="vacuum" coeffs="10" id="196" name="maximum y" type="y-plane" />
+  <surface boundary="vacuum" coeffs="-10" id="197" name="minimum z" type="z-plane" />
+  <surface boundary="vacuum" coeffs="10" id="198" name="maximum z" type="z-plane" />
+</geometry>
+<?xml version='1.0' encoding='utf-8'?>
+<materials>
+  <material depletable="true" id="31" name="fuel">
+    <density units="g/cc" value="4.5" />
+    <nuclide ao="1.0" name="U235" />
+  </material>
+  <material id="32" name="zircaloy">
+    <density units="g/cc" value="5.77" />
+    <nuclide ao="0.5145" name="Zr90" />
+    <nuclide ao="0.1122" name="Zr91" />
+    <nuclide ao="0.1715" name="Zr92" />
+    <nuclide ao="0.1738" name="Zr94" />
+    <nuclide ao="0.028" name="Zr96" />
+  </material>
+  <material id="33" name="water">
+    <density units="atom/b-cm" value="0.07416" />
+    <nuclide ao="2.0" name="H1" />
+    <nuclide ao="1.0" name="O16" />
+  </material>
+</materials>
+<?xml version='1.0' encoding='utf-8'?>
+<settings>
+  <run_mode>fixed source</run_mode>
+  <particles>100</particles>
+  <batches>10</batches>
+  <source strength="1.0">
+    <space origin="0.0 0.0 0.0" type="spherical">
+      <r parameters="0.0 0.0" type="uniform" />
+      <theta type="discrete">
+        <parameters>0.0 1.0</parameters>
+      </theta>
+      <phi type="discrete">
+        <parameters>0.0 1.0</parameters>
+      </phi>
+    </space>
+    <angle reference_uvw="-1.0 0.0 0.0" type="monodirectional" />
+    <energy type="discrete">
+      <parameters>15000000.0 1.0</parameters>
+    </energy>
+  </source>
+</settings>
+<?xml version='1.0' encoding='utf-8'?>
+<tallies>
+  <mesh id="21">
+    <dimension>10 10 10</dimension>
+    <lower_left>-10.0 -10.0 -10.0</lower_left>
+    <upper_right>10.0 10.0 10.0</upper_right>
+  </mesh>
+  <mesh id="22" library="moab" type="unstructured">
+    <filename>test_mesh_tets_w_holes.exo</filename>
+  </mesh>
+  <filter id="21" type="mesh">
+    <bins>21</bins>
+  </filter>
+  <filter id="22" type="mesh">
+    <bins>22</bins>
+  </filter>
+  <tally id="21" name="regular mesh tally">
+    <filters>21</filters>
+    <scores>flux</scores>
+    <estimator>tracklength</estimator>
+  </tally>
+  <tally id="22" name="unstructured mesh tally">
+    <filters>22</filters>
+    <scores>flux</scores>
+    <estimator>tracklength</estimator>
+  </tally>
+</tallies>
diff --git a/tests/regression_tests/unstructured_mesh/inputs_true15.dat b/tests/regression_tests/unstructured_mesh/inputs_true15.dat
new file mode 100644
index 0000000000..4ef681bc80
--- /dev/null
+++ b/tests/regression_tests/unstructured_mesh/inputs_true15.dat
@@ -0,0 +1,92 @@
+<?xml version='1.0' encoding='utf-8'?>
+<geometry>
+  <cell id="34" material="34" name="fuel" region="199 -200 201 -202 203 -204" universe="12" />
+  <cell id="35" material="35" name="clad" region="(-199 | 200 | -201 | 202 | -203 | 204) (205 -206 207 -208 209 -210)" universe="12" />
+  <cell id="36" material="36" name="water" region="(-205 | 206 | -207 | 208 | -209 | 210) (211 -212 213 -214 215 -216)" universe="12" />
+  <surface coeffs="-5.0" id="199" name="minimum x" type="x-plane" />
+  <surface coeffs="5.0" id="200" name="maximum x" type="x-plane" />
+  <surface coeffs="-5.0" id="201" name="minimum y" type="y-plane" />
+  <surface coeffs="5.0" id="202" name="maximum y" type="y-plane" />
+  <surface coeffs="-5.0" id="203" name="minimum z" type="z-plane" />
+  <surface coeffs="5.0" id="204" name="maximum z" type="z-plane" />
+  <surface coeffs="-6.0" id="205" name="minimum x" type="x-plane" />
+  <surface coeffs="6.0" id="206" name="maximum x" type="x-plane" />
+  <surface coeffs="-6.0" id="207" name="minimum y" type="y-plane" />
+  <surface coeffs="6.0" id="208" name="maximum y" type="y-plane" />
+  <surface coeffs="-6.0" id="209" name="minimum z" type="z-plane" />
+  <surface coeffs="6.0" id="210" name="maximum z" type="z-plane" />
+  <surface boundary="vacuum" coeffs="-10" id="211" name="minimum x" type="x-plane" />
+  <surface boundary="vacuum" coeffs="10" id="212" name="maximum x" type="x-plane" />
+  <surface boundary="vacuum" coeffs="-10" id="213" name="minimum y" type="y-plane" />
+  <surface boundary="vacuum" coeffs="10" id="214" name="maximum y" type="y-plane" />
+  <surface boundary="vacuum" coeffs="-10" id="215" name="minimum z" type="z-plane" />
+  <surface boundary="vacuum" coeffs="10" id="216" name="maximum z" type="z-plane" />
+</geometry>
+<?xml version='1.0' encoding='utf-8'?>
+<materials>
+  <material depletable="true" id="34" name="fuel">
+    <density units="g/cc" value="4.5" />
+    <nuclide ao="1.0" name="U235" />
+  </material>
+  <material id="35" name="zircaloy">
+    <density units="g/cc" value="5.77" />
+    <nuclide ao="0.5145" name="Zr90" />
+    <nuclide ao="0.1122" name="Zr91" />
+    <nuclide ao="0.1715" name="Zr92" />
+    <nuclide ao="0.1738" name="Zr94" />
+    <nuclide ao="0.028" name="Zr96" />
+  </material>
+  <material id="36" name="water">
+    <density units="atom/b-cm" value="0.07416" />
+    <nuclide ao="2.0" name="H1" />
+    <nuclide ao="1.0" name="O16" />
+  </material>
+</materials>
+<?xml version='1.0' encoding='utf-8'?>
+<settings>
+  <run_mode>fixed source</run_mode>
+  <particles>100</particles>
+  <batches>10</batches>
+  <source strength="1.0">
+    <space origin="0.0 0.0 0.0" type="spherical">
+      <r parameters="0.0 0.0" type="uniform" />
+      <theta type="discrete">
+        <parameters>0.0 1.0</parameters>
+      </theta>
+      <phi type="discrete">
+        <parameters>0.0 1.0</parameters>
+      </phi>
+    </space>
+    <angle reference_uvw="-1.0 0.0 0.0" type="monodirectional" />
+    <energy type="discrete">
+      <parameters>15000000.0 1.0</parameters>
+    </energy>
+  </source>
+</settings>
+<?xml version='1.0' encoding='utf-8'?>
+<tallies>
+  <mesh id="23">
+    <dimension>10 10 10</dimension>
+    <lower_left>-10.0 -10.0 -10.0</lower_left>
+    <upper_right>10.0 10.0 10.0</upper_right>
+  </mesh>
+  <mesh id="24" library="moab" type="unstructured">
+    <filename>test_mesh_tets.exo</filename>
+  </mesh>
+  <filter id="23" type="mesh">
+    <bins>23</bins>
+  </filter>
+  <filter id="24" type="mesh">
+    <bins>24</bins>
+  </filter>
+  <tally id="23" name="regular mesh tally">
+    <filters>23</filters>
+    <scores>flux</scores>
+    <estimator>tracklength</estimator>
+  </tally>
+  <tally id="24" name="unstructured mesh tally">
+    <filters>24</filters>
+    <scores>flux</scores>
+    <estimator>tracklength</estimator>
+  </tally>
+</tallies>
diff --git a/tests/regression_tests/unstructured_mesh/inputs_true2.dat b/tests/regression_tests/unstructured_mesh/inputs_true2.dat
index 3902f36b58..a93b8a160e 100644
--- a/tests/regression_tests/unstructured_mesh/inputs_true2.dat
+++ b/tests/regression_tests/unstructured_mesh/inputs_true2.dat
@@ -70,8 +70,8 @@
     <lower_left>-10.0 -10.0 -10.0</lower_left>
     <upper_right>10.0 10.0 10.0</upper_right>
   </mesh>
-  <mesh id="6" library="moab" type="unstructured">
-    <filename>test_mesh_tets_w_holes.h5m</filename>
+  <mesh id="6" library="libmesh" type="unstructured">
+    <filename>test_mesh_tets_w_holes.exo</filename>
   </mesh>
   <filter id="5" type="mesh">
     <bins>5</bins>
diff --git a/tests/regression_tests/unstructured_mesh/inputs_true3.dat b/tests/regression_tests/unstructured_mesh/inputs_true3.dat
index 2bb59617bd..baa197a68e 100644
--- a/tests/regression_tests/unstructured_mesh/inputs_true3.dat
+++ b/tests/regression_tests/unstructured_mesh/inputs_true3.dat
@@ -70,8 +70,8 @@
     <lower_left>-10.0 -10.0 -10.0</lower_left>
     <upper_right>10.0 10.0 10.0</upper_right>
   </mesh>
-  <mesh id="8" library="moab" type="unstructured">
-    <filename>test_mesh_tets.h5m</filename>
+  <mesh id="8" library="libmesh" type="unstructured">
+    <filename>test_mesh_tets.exo</filename>
   </mesh>
   <filter id="7" type="mesh">
     <bins>7</bins>
diff --git a/tests/regression_tests/unstructured_mesh/inputs_true4.dat b/tests/regression_tests/unstructured_mesh/inputs_true4.dat
index ee89864654..a39452da7c 100644
--- a/tests/regression_tests/unstructured_mesh/inputs_true4.dat
+++ b/tests/regression_tests/unstructured_mesh/inputs_true4.dat
@@ -71,7 +71,7 @@
     <upper_right>10.0 10.0 10.0</upper_right>
   </mesh>
   <mesh id="10" library="moab" type="unstructured">
-    <filename>test_mesh_tets_w_holes.h5m</filename>
+    <filename>test_mesh_tets_w_holes.exo</filename>
   </mesh>
   <filter id="9" type="mesh">
     <bins>9</bins>
diff --git a/tests/regression_tests/unstructured_mesh/inputs_true5.dat b/tests/regression_tests/unstructured_mesh/inputs_true5.dat
index 0348bbd68e..288b7d1fcb 100644
--- a/tests/regression_tests/unstructured_mesh/inputs_true5.dat
+++ b/tests/regression_tests/unstructured_mesh/inputs_true5.dat
@@ -71,7 +71,7 @@
     <upper_right>10.0 10.0 10.0</upper_right>
   </mesh>
   <mesh id="12" library="moab" type="unstructured">
-    <filename>test_mesh_tets.h5m</filename>
+    <filename>test_mesh_tets.exo</filename>
   </mesh>
   <filter id="11" type="mesh">
     <bins>11</bins>
diff --git a/tests/regression_tests/unstructured_mesh/inputs_true6.dat b/tests/regression_tests/unstructured_mesh/inputs_true6.dat
index eb7f5e4153..883e6cbf48 100644
--- a/tests/regression_tests/unstructured_mesh/inputs_true6.dat
+++ b/tests/regression_tests/unstructured_mesh/inputs_true6.dat
@@ -71,7 +71,7 @@
     <upper_right>10.0 10.0 10.0</upper_right>
   </mesh>
   <mesh id="14" library="moab" type="unstructured">
-    <filename>test_mesh_tets_w_holes.h5m</filename>
+    <filename>test_mesh_tets_w_holes.exo</filename>
   </mesh>
   <filter id="13" type="mesh">
     <bins>13</bins>
diff --git a/tests/regression_tests/unstructured_mesh/inputs_true7.dat b/tests/regression_tests/unstructured_mesh/inputs_true7.dat
index 931c6a3ee8..267966e3ca 100644
--- a/tests/regression_tests/unstructured_mesh/inputs_true7.dat
+++ b/tests/regression_tests/unstructured_mesh/inputs_true7.dat
@@ -71,7 +71,7 @@
     <upper_right>10.0 10.0 10.0</upper_right>
   </mesh>
   <mesh id="16" library="moab" type="unstructured">
-    <filename>test_mesh_tets.h5m</filename>
+    <filename>test_mesh_tets.exo</filename>
   </mesh>
   <filter id="15" type="mesh">
     <bins>15</bins>
diff --git a/tests/regression_tests/unstructured_mesh/inputs_true8.dat b/tests/regression_tests/unstructured_mesh/inputs_true8.dat
new file mode 100644
index 0000000000..ff3d3dc8d5
--- /dev/null
+++ b/tests/regression_tests/unstructured_mesh/inputs_true8.dat
@@ -0,0 +1,92 @@
+<?xml version='1.0' encoding='utf-8'?>
+<geometry>
+  <cell id="13" material="13" name="fuel" region="73 -74 75 -76 77 -78" universe="5" />
+  <cell id="14" material="14" name="clad" region="(-73 | 74 | -75 | 76 | -77 | 78) (79 -80 81 -82 83 -84)" universe="5" />
+  <cell id="15" material="15" name="water" region="(-79 | 80 | -81 | 82 | -83 | 84) (85 -86 87 -88 89 -90)" universe="5" />
+  <surface coeffs="-5.0" id="73" name="minimum x" type="x-plane" />
+  <surface coeffs="5.0" id="74" name="maximum x" type="x-plane" />
+  <surface coeffs="-5.0" id="75" name="minimum y" type="y-plane" />
+  <surface coeffs="5.0" id="76" name="maximum y" type="y-plane" />
+  <surface coeffs="-5.0" id="77" name="minimum z" type="z-plane" />
+  <surface coeffs="5.0" id="78" name="maximum z" type="z-plane" />
+  <surface coeffs="-6.0" id="79" name="minimum x" type="x-plane" />
+  <surface coeffs="6.0" id="80" name="maximum x" type="x-plane" />
+  <surface coeffs="-6.0" id="81" name="minimum y" type="y-plane" />
+  <surface coeffs="6.0" id="82" name="maximum y" type="y-plane" />
+  <surface coeffs="-6.0" id="83" name="minimum z" type="z-plane" />
+  <surface coeffs="6.0" id="84" name="maximum z" type="z-plane" />
+  <surface boundary="vacuum" coeffs="-15" id="85" name="minimum x" type="x-plane" />
+  <surface boundary="vacuum" coeffs="15" id="86" name="maximum x" type="x-plane" />
+  <surface boundary="vacuum" coeffs="-15" id="87" name="minimum y" type="y-plane" />
+  <surface boundary="vacuum" coeffs="15" id="88" name="maximum y" type="y-plane" />
+  <surface boundary="vacuum" coeffs="-15" id="89" name="minimum z" type="z-plane" />
+  <surface boundary="vacuum" coeffs="15" id="90" name="maximum z" type="z-plane" />
+</geometry>
+<?xml version='1.0' encoding='utf-8'?>
+<materials>
+  <material depletable="true" id="13" name="fuel">
+    <density units="g/cc" value="4.5" />
+    <nuclide ao="1.0" name="U235" />
+  </material>
+  <material id="14" name="zircaloy">
+    <density units="g/cc" value="5.77" />
+    <nuclide ao="0.5145" name="Zr90" />
+    <nuclide ao="0.1122" name="Zr91" />
+    <nuclide ao="0.1715" name="Zr92" />
+    <nuclide ao="0.1738" name="Zr94" />
+    <nuclide ao="0.028" name="Zr96" />
+  </material>
+  <material id="15" name="water">
+    <density units="atom/b-cm" value="0.07416" />
+    <nuclide ao="2.0" name="H1" />
+    <nuclide ao="1.0" name="O16" />
+  </material>
+</materials>
+<?xml version='1.0' encoding='utf-8'?>
+<settings>
+  <run_mode>fixed source</run_mode>
+  <particles>100</particles>
+  <batches>10</batches>
+  <source strength="1.0">
+    <space origin="0.0 0.0 0.0" type="spherical">
+      <r parameters="0.0 0.0" type="uniform" />
+      <theta type="discrete">
+        <parameters>0.0 1.0</parameters>
+      </theta>
+      <phi type="discrete">
+        <parameters>0.0 1.0</parameters>
+      </phi>
+    </space>
+    <angle reference_uvw="-1.0 0.0 0.0" type="monodirectional" />
+    <energy type="discrete">
+      <parameters>15000000.0 1.0</parameters>
+    </energy>
+  </source>
+</settings>
+<?xml version='1.0' encoding='utf-8'?>
+<tallies>
+  <mesh id="9">
+    <dimension>10 10 10</dimension>
+    <lower_left>-10.0 -10.0 -10.0</lower_left>
+    <upper_right>10.0 10.0 10.0</upper_right>
+  </mesh>
+  <mesh id="10" library="moab" type="unstructured">
+    <filename>test_mesh_tets_w_holes.exo</filename>
+  </mesh>
+  <filter id="9" type="mesh">
+    <bins>9</bins>
+  </filter>
+  <filter id="10" type="mesh">
+    <bins>10</bins>
+  </filter>
+  <tally id="9" name="regular mesh tally">
+    <filters>9</filters>
+    <scores>flux</scores>
+    <estimator>collision</estimator>
+  </tally>
+  <tally id="10" name="unstructured mesh tally">
+    <filters>10</filters>
+    <scores>flux</scores>
+    <estimator>collision</estimator>
+  </tally>
+</tallies>
diff --git a/tests/regression_tests/unstructured_mesh/inputs_true9.dat b/tests/regression_tests/unstructured_mesh/inputs_true9.dat
new file mode 100644
index 0000000000..953750e5ca
--- /dev/null
+++ b/tests/regression_tests/unstructured_mesh/inputs_true9.dat
@@ -0,0 +1,92 @@
+<?xml version='1.0' encoding='utf-8'?>
+<geometry>
+  <cell id="16" material="16" name="fuel" region="91 -92 93 -94 95 -96" universe="6" />
+  <cell id="17" material="17" name="clad" region="(-91 | 92 | -93 | 94 | -95 | 96) (97 -98 99 -100 101 -102)" universe="6" />
+  <cell id="18" material="18" name="water" region="(-97 | 98 | -99 | 100 | -101 | 102) (103 -104 105 -106 107 -108)" universe="6" />
+  <surface coeffs="-5.0" id="91" name="minimum x" type="x-plane" />
+  <surface coeffs="5.0" id="92" name="maximum x" type="x-plane" />
+  <surface coeffs="-5.0" id="93" name="minimum y" type="y-plane" />
+  <surface coeffs="5.0" id="94" name="maximum y" type="y-plane" />
+  <surface coeffs="-5.0" id="95" name="minimum z" type="z-plane" />
+  <surface coeffs="5.0" id="96" name="maximum z" type="z-plane" />
+  <surface coeffs="-6.0" id="97" name="minimum x" type="x-plane" />
+  <surface coeffs="6.0" id="98" name="maximum x" type="x-plane" />
+  <surface coeffs="-6.0" id="99" name="minimum y" type="y-plane" />
+  <surface coeffs="6.0" id="100" name="maximum y" type="y-plane" />
+  <surface coeffs="-6.0" id="101" name="minimum z" type="z-plane" />
+  <surface coeffs="6.0" id="102" name="maximum z" type="z-plane" />
+  <surface boundary="vacuum" coeffs="-15" id="103" name="minimum x" type="x-plane" />
+  <surface boundary="vacuum" coeffs="15" id="104" name="maximum x" type="x-plane" />
+  <surface boundary="vacuum" coeffs="-15" id="105" name="minimum y" type="y-plane" />
+  <surface boundary="vacuum" coeffs="15" id="106" name="maximum y" type="y-plane" />
+  <surface boundary="vacuum" coeffs="-15" id="107" name="minimum z" type="z-plane" />
+  <surface boundary="vacuum" coeffs="15" id="108" name="maximum z" type="z-plane" />
+</geometry>
+<?xml version='1.0' encoding='utf-8'?>
+<materials>
+  <material depletable="true" id="16" name="fuel">
+    <density units="g/cc" value="4.5" />
+    <nuclide ao="1.0" name="U235" />
+  </material>
+  <material id="17" name="zircaloy">
+    <density units="g/cc" value="5.77" />
+    <nuclide ao="0.5145" name="Zr90" />
+    <nuclide ao="0.1122" name="Zr91" />
+    <nuclide ao="0.1715" name="Zr92" />
+    <nuclide ao="0.1738" name="Zr94" />
+    <nuclide ao="0.028" name="Zr96" />
+  </material>
+  <material id="18" name="water">
+    <density units="atom/b-cm" value="0.07416" />
+    <nuclide ao="2.0" name="H1" />
+    <nuclide ao="1.0" name="O16" />
+  </material>
+</materials>
+<?xml version='1.0' encoding='utf-8'?>
+<settings>
+  <run_mode>fixed source</run_mode>
+  <particles>100</particles>
+  <batches>10</batches>
+  <source strength="1.0">
+    <space origin="0.0 0.0 0.0" type="spherical">
+      <r parameters="0.0 0.0" type="uniform" />
+      <theta type="discrete">
+        <parameters>0.0 1.0</parameters>
+      </theta>
+      <phi type="discrete">
+        <parameters>0.0 1.0</parameters>
+      </phi>
+    </space>
+    <angle reference_uvw="-1.0 0.0 0.0" type="monodirectional" />
+    <energy type="discrete">
+      <parameters>15000000.0 1.0</parameters>
+    </energy>
+  </source>
+</settings>
+<?xml version='1.0' encoding='utf-8'?>
+<tallies>
+  <mesh id="11">
+    <dimension>10 10 10</dimension>
+    <lower_left>-10.0 -10.0 -10.0</lower_left>
+    <upper_right>10.0 10.0 10.0</upper_right>
+  </mesh>
+  <mesh id="12" library="moab" type="unstructured">
+    <filename>test_mesh_tets.exo</filename>
+  </mesh>
+  <filter id="11" type="mesh">
+    <bins>11</bins>
+  </filter>
+  <filter id="12" type="mesh">
+    <bins>12</bins>
+  </filter>
+  <tally id="11" name="regular mesh tally">
+    <filters>11</filters>
+    <scores>flux</scores>
+    <estimator>collision</estimator>
+  </tally>
+  <tally id="12" name="unstructured mesh tally">
+    <filters>12</filters>
+    <scores>flux</scores>
+    <estimator>collision</estimator>
+  </tally>
+</tallies>
diff --git a/tests/regression_tests/unstructured_mesh/test.py b/tests/regression_tests/unstructured_mesh/test.py
index 39259a2fec..d1a013561b 100644
--- a/tests/regression_tests/unstructured_mesh/test.py
+++ b/tests/regression_tests/unstructured_mesh/test.py
@@ -62,17 +62,20 @@ class UnstructuredMeshTest(PyAPITestHarness):
     def _cleanup(self):
         super()._cleanup()
         output = glob.glob('tally*.vtk')
+        output += glob.glob('tally*.e')
         for f in output:
             if os.path.exists(f):
                 os.remove(f)
 
 
-param_values = (['collision', 'tracklength'], # estimators
+param_values = (['libmesh', 'moab'], # mesh libraries
+                ['collision', 'tracklength'], # estimators
                 [True, False], # geometry outside of the mesh
                 [(333, 90, 77), None]) # location of holes in the mesh
 test_cases = []
-for i, (estimator, ext_geom, holes) in enumerate(product(*param_values)):
-    test_cases.append({'estimator' : estimator,
+for i, (lib, estimator, ext_geom, holes) in enumerate(product(*param_values)):
+    test_cases.append({'library' : lib,
+                       'estimator' : estimator,
                        'external_geom' : ext_geom,
                        'holes' : holes,
                        'inputs_true' : 'inputs_true{}.dat'.format(i)})
@@ -81,6 +84,11 @@ for i, (estimator, ext_geom, holes) in enumerate(product(*param_values)):
 @pytest.mark.parametrize("test_opts", test_cases)
 def test_unstructured_mesh(test_opts):
 
+    # skip the tracklength test for libmesh
+    if test_opts['library'] == 'libmesh' and \
+       test_opts['estimator'] == 'tracklength':
+       pytest.skip("Tracklength tallies are not supported using libmesh.")
+
     ### Materials ###
     materials = openmc.Materials()
 
@@ -185,12 +193,12 @@ def test_unstructured_mesh(test_opts):
     regular_mesh_filter = openmc.MeshFilter(mesh=regular_mesh)
 
     if test_opts['holes']:
-        mesh_filename = "test_mesh_tets_w_holes.h5m"
+        mesh_filename = "test_mesh_tets_w_holes.exo"
     else:
-        mesh_filename = "test_mesh_tets.h5m"
+        mesh_filename = "test_mesh_tets.exo"
 
     uscd_mesh = openmc.UnstructuredMesh(mesh_filename)
-    uscd_mesh.library = 'moab'
+    uscd_mesh.library = test_opts['library']
     uscd_filter = openmc.MeshFilter(mesh=uscd_mesh)
 
     # create tallies
diff --git a/tests/regression_tests/unstructured_mesh/test_mesh_tets.exo b/tests/regression_tests/unstructured_mesh/test_mesh_tets.exo
new file mode 100644
index 0000000000..90e7473603
Binary files /dev/null and b/tests/regression_tests/unstructured_mesh/test_mesh_tets.exo differ
diff --git a/tests/regression_tests/unstructured_mesh/test_mesh_tets.h5m b/tests/regression_tests/unstructured_mesh/test_mesh_tets.h5m
deleted file mode 100644
index dc573142f6..0000000000
Binary files a/tests/regression_tests/unstructured_mesh/test_mesh_tets.h5m and /dev/null differ
diff --git a/tests/regression_tests/unstructured_mesh/test_mesh_tets_w_holes.exo b/tests/regression_tests/unstructured_mesh/test_mesh_tets_w_holes.exo
new file mode 100644
index 0000000000..3c30a55dc8
Binary files /dev/null and b/tests/regression_tests/unstructured_mesh/test_mesh_tets_w_holes.exo differ
diff --git a/tests/regression_tests/unstructured_mesh/test_mesh_tets_w_holes.h5m b/tests/regression_tests/unstructured_mesh/test_mesh_tets_w_holes.h5m
deleted file mode 100644
index 971de0ad3c..0000000000
Binary files a/tests/regression_tests/unstructured_mesh/test_mesh_tets_w_holes.h5m and /dev/null differ