Term | Definition |
Parent (Protolith) | the rock type that was metamorphosed |
Recrystallization | process whereby small crystals of one mineral will slowly convert to fewer, larger crystals of the same mineral, without melting of the rock |
Neomorphism | Minerals not only recrystallize but, also form different minerals from the same chemical elements. |
Texture | a description of its constituent parts and their sizes, shapes, and arrangements |
Slaty rock cleavage | flat foliation developed along flat, parallel, closely spaced shear planes in tightly folded clay- or mica- rich rocks
--flat-- |
Slaty rock cleavage [foliated or non-foliated] | foliated |
Slaty rock cleavage [rocks] | muscovite, chlorite |
Phyllite texture | a wavy and/or wrinkled foliation of fine-grained platy minerals that gives the rock a satiny or metallic luster; normally developed or perpendicular to a weak slaty cleavage, and it is a product of intermediate-grade metamorphism
--wavy, wrinkled-- |
Phyllite texture [foliated or non-foliated] | foliated |
Phyllite texture [rocks] | muscovite, chlorite |
Schistosity | scaly glittery layering of visible (medium to coarse-grained) platy minerals a/o linear alignment of long prismatic crystals; break along foliations; a product of intermediate-to-high grades of metamorphism
--slaty, glittery-- |
Schistosity [foliated or non-foliated] | foliated |
Schistosity [rocks] | micas, chlorite, tourmaline, hornblende, kyanite |
Gneissic banding | alternating layers of light & dark medium to coarse-grained minerals; Most form by high-grade metamorphism (including recrystallization) of clay or mica-rich rocks [shale] or igneous rocks [granite and dorite]
--layers-- |
Gneissic banding [foliated or non-foliated] | foliated |
Gneissic banding [rocks] | ferromagnesian-->dark bands &
quartz, feldspars-->light bands |
Crystalline texture | a medium- to coarse-grained aggregate of intergrown, usually equal-sized (equigranular), visible crystals.
--equigranular-- |
Crystalline texture [foliated or non-foliated] | non-foliated |
Crystalline texture [rocks] | marble |
Microcrystalline texture | a fine-grained aggregate of intergrown microscopic crystals.
--intergrown-- |
Microcrystalline texture [foliated or non-foliated] | non-foliated |
Microcrystalline texture [rocks] | Hornfels |
Sandy texture | a medium- to coarse-grained aggregate of fused, sand-sized grains that resembles sandstone
--fused-- |
Sandy texture [foliated or non-foliated] | non-foliated |
Sandy texture [rocks] | quartzite |
Glassy texture | a homogeneous texture with no visible grains or other structures and breaks along glossy surfaces
--no visible crystals-- |
Glassy texture [foliated or non-foliated] | non-foliated |
Glassy texture [rocks] | anthracite coal |
Polymorphs | minerals have the same chemical composition but different crystalline structure and physical properties that can be used to distinguish them. |
foliation | layering and parallel alignment of platy (flat) mineral crystals |
non-foliation | no obvious layering; may exhibit stretched fossils or long, prismatic crystals that have grown parallel to the pressure field |