Which term is defined as a crystal shape with eight equal triangular faces?

Which term is defined as a crystal shape with eight equal triangular faces?

• A. Graining (Grain Lines)
• B. Octahedron
• C. Growth Marks
• D. Resorption

Answer: (B)

Eight equal triangular faces describe an octahedron. In diamond crystals, the octahedral crystal form is a common habit, a regular polyhedron whose eight faces are all equilateral triangles and which is the dual of the cube. This makes it the best match for a crystal shape defined by eight triangular faces. The other terms refer to surface or internal features rather than a geometric form: graining are internal growth lines, growth marks are surface indications of rapid growth, and resorption is the dissolution of crystal surfaces.

Eight equal triangular faces describe an octahedron. In diamond crystals, the octahedral crystal form is a common habit, a regular polyhedron whose eight faces are all equilateral triangles and which is the dual of the cube. This makes it the best match for a crystal shape defined by eight triangular faces. The other terms refer to surface or internal features rather than a geometric form: graining are internal growth lines, growth marks are surface indications of rapid growth, and resorption is the dissolution of crystal surfaces.