- T
-
- Tabular
- Tarnish
- Tectosilicates (subgroup)
- Tellurides (subgroup)
- Tenacity
- Termination
- Tetragonal (crystal
system)
- Tetrahedral
- Tetrahedron (shape)
- Tetrahedron (silicates)
- Tetragonal trisoctahedron
- Texture
- Thermoluminescence
- Thermoluminescent
- Transformation
- Transparency
- Transparent
- Translucency
- Translucent
- Trapezohedral
- Trapezohedron
- Trap rock
- Triboluminescence
- Triboluminescent
- Trichroic
- Trichroism
- Triclinic (crystal system)
- Trigonal (crystal system)
- Trilling
- Triplet
- Trisoctahedral
- Trisoctahedron
- Trunk
- Tube test
- Tuberose
- Tufa
- Tufacious spring
- Tuff
- Tumbled
- Tumbler
- Tungstates (group)
- Tungstens
- Twin
- Twinned crystal
- Twinning