AMPHIBOLITE

Foliated or nonfoliated

Medium to coarse grained

Mostly visible crystals of amphibole (usually glossy black hornblende)

Parent: basalt, gabbro, ultramafic igneous rock

GNEISS

Foliated

Medium to coarse grained

Banding; minerals segregated into alternating layers for banded texture; crystalline texture

Visible crystals of two or more minerals in alternating dark and light layers

HORNFELS

Nonfoliated

Fine grained or no visible grains

Microcrystalline texture

Usually dull, dark color; very hard

Parent: any type rock

MARBLE

Nonfoliated

Fine to coarse grained

Microcrystalline (sugar cube) or medium to coarse crystalline texture

Calcite (or dolomite) crystals of nearly equal size fused together; calcite effervesces in dilute HCl; dolomite effervesces if powdered

Parent: Limestone

METACONGLOMERATE

Nonfoliated

Fine to coarse grained

Conglomeratic texture, but breaks across grains

Pebbles may be stretched or cut by rock clevage

Parent: Conglomerate

PHYLLITE

Foliated

Fine grained or no visible grains

Texture well developed, more than slaty cleavage

Breaks along wrinkled or wavy folliation surfaces with shiny metallic luster

Has a sheen

QUARTZITE

Nonfoliated

Fine to coarse grained

Sandy texture

Quartz sand grains fused together; won't rub off; usually light colored

Parent: sandstone

SCHIST

Foliated

Medium to coarse grained

Foliation formed by alignment of visible crystals; rock breaks along scaly foliation surfaces; crystalline texture

Visible sparkling crystals of platy minerals (chlorite, biotite, muscovite), bladed crystals, or prismatic crystals

Parent: mudstone, shale, slate, or phyllite

SERPENTINITE

Nonfoliated

Fine grained to no visible grains

Microcrystalline texture or no visible grains; may have fibrous asbestos form

Dull or glossy; color usually shades of green

Parent: basalt, gabbro, or ultramafic igneous rock

SLATE

Foliated

Flat slaty cleavage well developed

Dull luster; breaks into hard flat sheets

Parent: mudstone or shale

SOAPSTONE

Nonfoliated

Microcrystalline or no visible grains

Talc; can be scratched with fingernail

Shades of green, gray, brown, white

Parent: basalt, gabbro, or ultramafic igneous rocks