General Rock Type Texture - ave.

size of minerals General color and/or composition - Miscellaneous observations Rock Name

IGNEOUS

ROCKS Interlocking

homogenous

crystalline

texture - no

preferred

orientation to the

mineral grains Fine grained Extrusive, volcanic Felsic - Light colored Rhyolite

Intermediate Andesite

Mafic - Dark colored Basalt

Medium grained Dikes, sills, etc. Felsic - Light colored - - - - - -

Intermediate Dacite

Mafic - Dark colored Diabase

Coarse grained Generally intrusive Felsic - Light colored Granite

Intermediate Diorite

Mafic - Dark colored Gabbro

Ultramafic Peridotite

Glassy Dark to black - felsic (DOES NOT

follow normal color index) Obsidian

Frothy Felsic - Light colored Pumice

Mafic - Dark colored Scoria

SEDIMENTARY

ROCKS Consolidated detrital clasts, chemical precipitates, and/or biological residue Coarse Fragments Rounded clasts Conglomerate

Angular clasts Breccia

Sand sized fragments Clean quartz (w/feldspar?) Sandstone

Dirty w/rock fragments & clay Graywacke

Fine grained - cannot see individual clasts Nonfoliated, "clay the size" Siltstone

Foliated, "clay the mineral" Shale

Chemical - fine grain Soft - passes fizz test Limestone

Hard - fails fizz test Chert

Fossiliferous Mostly shell fragments Coquina

METAMORPHIC

ROCKS Interlocking non- homogenous crystalline texture - commonly with a preferred orientation to the mineral grains F O L I A T E D Very fine grained-no visible minerals Dull - passes "tink test" Slate

Foliated, shiny due to increased size of micaceous minerals (almost see them) Phyllite

Medium to coarse grain Individual mineral grains visible. Major mineral(s) included as name modifiers Schist

(ex. Mica Schist)

Color banded Alternating layers of light (felsic)

and dark (mafic) minerals Gneiss

Distinct layering - often highly folded and contorted Alternating layers of felsic igneous rock (light) and mafic gneiss (dark) Migmatite

Non-foliated, with non-oriented grains Soft - passes fizz test Marble

Hard - fails fizz test Quartzite