Rock and Mineral Identification Study Guide

Pyrite

An iron sulfide mineral with a metallic luster, brass/gold color, and a hardness of 6-6.5.

Chalcopyrite

A copper-iron sulfide mineral characterized by a metallic luster, silvery/gold color, and hardness of 3.5-4.

Magnetite

An iron oxide mineral that is magnetic, metallic, grey/black in color, and has a hardness of 6-6.5.

Hematite

An iron oxide mineral that can be either metallic or non-metallic with a hardness of 5-6 and typically red/brown in color.

Garnet

A complex silicate mineral that is non-metallic, vitreous, and has a hardness of 6.5-7, often dark red or black.

Quartz

A silicon dioxide mineral that is non-metallic, vitreous, and has a hardness of 7, commonly found in various colors.

Feldspar

A group of minerals including plagioclase and potassium feldspar, known for their non-metallic luster and hardness of 6.

Fluorite

A calcium fluoride mineral that is non-metallic, vitreous, with a hardness of 4, and can be fluorescent.

Muscovite

A potassium hydrous aluminum silicate with a non-metallic pearly luster, a hardness of 2-2.5, and typically colorless to yellow.

Biotite

A ferromagnesian potassium aluminum silicate that is non-metallic and pearly, with a hardness of 2.5-3 and black/brown color.

Kaolinite

An aluminum silicate hydroxide with an earthy luster, hardness of 1-2, and a powdery feel.

Gypsum

A hydrated calcium sulfate mineral that is silky, non-metallic, with a hardness of 2, and forms tabular crystals.

Calcite

A calcium carbonate mineral that is non-metallic, vitreous, and has a hardness of 3, reacting with hydrochloric acid.

Halite

A sodium chloride mineral that is non-metallic, vitreous, has a hardness of 2.5, and is known for its salt taste.

Olivine

A ferromagnesian silicate mineral that is non-metallic, vitreous, has a hardness of 6.5-7, and olive green/yellow in color.

Hornblende

A calcium ferromagnesian aluminum silicate that is non-metallic, vitreous, with a hardness of 5.5-6 and grey/black color.

Augite

A calcium ferromagnesian silicate that is non-metallic, vitreous, with a hardness of 5.5-6 and green/black color.

Obsidian

An extrusive felsic igneous rock characterized by glassy texture and conchoidal fracture.

Pumice

An extrusive felsic igneous rock with a vesicular texture, lower density, and ability to float.

Scoria

An extrusive igneous rock that is intermediate to mafic and has a vesicular texture, denser than pumice.

Granite

An intrusive felsic igneous rock with a phaneritic texture, consisting mainly of quartz and feldspar.

Diorite

An intrusive intermediate igneous rock with a phaneritic texture, containing quartz, feldspar, and hornblende.

Basalt

An extrusive mafic igneous rock that is aphanitic, often found with higher mafic mineral content.

Gabbro

An intrusive mafic igneous rock with a phaneritic texture, rich in mafic minerals such as augite and olivine.

Chert

A clastic sedimentary rock composed primarily of quartz, not reacting with HCl, often found in marine environments.

Breccia

A clastic sedimentary rock characterized by angular clasts and typically forms in alluvial environments.

Conglomerate

A clastic sedimentary rock composed of rounded clasts, commonly found in rivers and streams.

Siltstone

A clastic sedimentary rock made of silt-sized grains, typically found in marine depositional environments.

Slate

A foliated metamorphic rock with a fine grain and excellent cleavage, derived from shale or mudstone.

Marble

A non-foliated metamorphic rock formed from limestone, composed mainly of calcite and effervesces with HCl.

Schist

A foliated metamorphic rock characterized by schistosity and mineral alignment, derived from mudstone or shale.

Gneiss

A foliated metamorphic rock with banded texture created by the segregation of minerals into layers.