 home |
 committees |
 readings |
 images |
 addresses |
- Crystallinity - the degree or extent of crystallization.
- Holocrystalline - entirely crystalline.
- Hypocrystalline - partly crystalline and partly glassy.
- Holohyaline - wholly glassy.
- Phaneritic - crystals visible to the naked eye.
- Pegmatitic -- crystals > 20 mm.
- Coarse-grained - crystals > 20 mm., but < 5 mm.
- Medium grained - crystals > 5 mm., but < 1 mm.
- Fine-grained - crystals < 1 mm.
- Aphanitic - crystals not visible to the unaided eye. May be crystalline or glassy
- Felsitic - an aphanitic texture in an acid rock.
- Microcrystalline - microscopically crystalline.
- Euhedral - possesses crystal outline.
- Subhedral - possesses crystal outline in part only.
- Anhedral -lacks crystal outline
- Equant - equidimensional
- Tabular - two dimensions much greater than the third.
- Prismatic - one dimension much greater than the other two.
- Acicular - needle-like.
- Irregular - no definite form.
- Granular
- Idiomorphic granular - most grains are euhedral.
- Hypidiomorphic granular (granitic) - grains show crystal faces in part.
- Allotriomorphic granular - most grains are anhedral.
- Microgranular - microscopically granular.
- Orthophyric - feldspar occurs as short, stumpy, euhedral crystals.
- Pilotaxitic - a felty aggregate of tiny, lath-shaped crystals.
- Porphyritic - large crystals (phenocrysts) imbedded in a finer-grained or amorphous groundmass.
- Subporphyritic - intermediate between porphyritic and granular.
- glomeroporphyritic - a porphyritic texture comprised of clusters of phenocrysts.
- Seriate - an anisometric texture in which the sizes of the crystals vary gradually or in a continuous series.
- Poikilitic - small crystals enclosed by larger crystals.
- Ophitic or diabasic - plagioclase enclosed by augite.
- Intersertal - crystalline or amorphous material fills the interspaces between larger, closely packed crystals.
- Hyalopilitic - glass enclosing numerous microlites.
- Trachytic - subparallel, tabular crystals of feldspar in an aphanitic rock.
- Trachytoid - similar to trachytic, but in a phaneritic rock.
- Graphic - two mineral (e.g., quartz and orthoclase) intergrown so as to give a cunieform-like appearance.
- Micrographic (micropegmatitic or granophyric) - a microscopic-scale graphic texture.
- Myrmekitic - a wormy-like intergrowth of quartz and plagioclase.
- Perthitic - an intergrowth of potash feldspar and plagioclase.
Shapes of single crystals.