Rocks and Minerals Study Guide for Science Olympiad

Gneiss

Banded. Made up of granular mineral grains. It typically contains abundant quartz or feldspar minerals.

Marble

Coarse, crystalline. Variety of colors.

Phyllite

Made up mainly of very fine-grained mica. Typically lustrous and sometimes wrinkled.

Quartzite

Composed primarily of quartz. One of hardest rocks.

Schist [Garnet]

shimmery gold — looks like flakes or little fish scales. Contains little garnets.

Schist [Mica]

Mica appears in sheets or patches.

Slate

Fine-grained, dark gray. Sheets.

Andesite

Fine-grained. Usually gray, brown, or greenish.

Basalt

Dark-colored, fine-grained. Often pitted with gas bubble holes.

Diorite

Coarse grained.

Gabbro

Coarse-grained, dark-colored. Usually black or dark green in color and composed mainly of the minerals plagioclase and augite. Most abundant rock in the deep oceanic crust.

Granite

Light-colored with grains large enough to be visible with the unaided eye. Usually a red, pink, gray or white color with dark mineral grains visible throughout.

Obsidian

Volcanic glass with a smooth uniform texture that breaks with a conchoidal fracture. BLACK.

Pegmatite

Determined by HUGE grain size.

Pumice

Light-colored. Air bubbles.

Rhyolite

a light-colored, fine-grained, with bits of other minerals throughout.

Scoria

Dark-colored. Air bubbles. Light.

anthracite coal

-Sedimentary

-Forms from bituminous coal

-Has the highest energy content of all coals

-High Luster

arkose

-Very coarse sandstone, mostly quartz and feldspar, -usually pink or gray.

bituminous coal

-Softer Coal

-formed from lignite coal, medium/fine grain,

-alternating dull and shiny layers.

Breccia

Clastic, coarse sized grains, usually near-surface faults, angular clasts

chert

Chemical Rock, Made of quartz, microscopic grain,

lighter than flint, formed from silica

conglomerate

Clastic Rock, Very coarse grains, rounded pieces of rock, formed in rivers, beaches..

Coquina

Chemical/Biochemical Rock, visible shells, fragments loosely cemented, made of CALCITEEEE

diatomite

Biochemical rock, white, no Hcl reaction, similar to chalk

dolostone

-medium/fine grains.

-Formed in marine environments.

lignite coal

-Lowest rank of coal, brownish black, visible plant material, crumbly, organic rock.

(Limestone) Crystalline

a sedimentary rock consisting of more than 50% calcium carbonate (calcite - CaCO3), chemical rock, fine-coarse grained.

(limestone) fossiliferous

Formed by the accumulation and consolidation of macroscopic calcite fossils, made of calcite, Medium to coarse-grained, warm, shallow, marine environment, White/gray/pink.

(limestone) oolitic

-medium grain size, usually light colored.

(Limestone) Travertine

Generally banded, usually very fine grained, calcite carbonate composition, light colored.

sandstone

Super fine/medium quartz grained, similar sized grains, very common.

shale

very fine, silt and clay (mud) grain size, hardens into slate.

(limestone) chalk

Composed mostly of calcium carbonate with minor amounts of silt and clay. Chalky, white.

Albite

White, tan, or cream feldspar

Almandine

Dark red, garnet

Amazonite

The only green feldspar, glassy.

Apatite

Usually green or purple, but can be almost any color.

Like Beryl, but softer.

Aragonite

White, tan, colorless, powdery variety of calcite.

Augite

Nondescript black rock, greenish tinge and cleavage at a right angle.

Azurite

Blues, with streaks. Glossy.

Bauxite

Tan rock with orange, white, and brown pisoliths of aluminum, causing light weight. Dull.

Barite

White and kind of platy, but very heavy because it contains barium.

Beryl

Light green and opaque, glassy.

Biotite

dark brown to black mica, vitreous, glassy.

Bornite

Dark, purplish-blue tarnish. metallic luster.

Calcite

Looks almost like fluorite and can be any color, but it's a little softer and it has a more rhombus like shape. DISSOLVES IN HCI ACID.

Celestite

Usually a soft, translucent white or blue.

Chalcopyrite

Very brassy yellow, tarnishes bright red, purple, yellow, and orange.

Copper

Usually has green tarnish.

Corundum

Very hard reddish or purplish rock, Often has small column-like opaque crystals. Vitreous.

Diamond

Hardest.

Dolomite

Thin, platy cream-colored crystals possibly has black specks between crystals.

Epidote

Greenish-yellow and grainy.

Feldspar

Salmon-pink color

Fluorite

Almost any color, a little harder than calcite, usually has dipyramidal or cubic structure. Fluorescent.

Galena

Perfect cubic cleavage and is very heavy. State mineral.

Limonite

Slightly iridescent tarnish, brownish, orange-black.

Gold

Smoother than pyrite, gold colored. metallic.

Graphite

Silver, shiny, soft, and leaves dark smudges on your hands.

Gypsum [Alabaster]

White and opaque, very soft and easily scratched with your fingernail.

Gypsum [Satin-Spar]

White and fibrous, very soft and easily scratched with your fingernail

Gypsum [Selenite]

Transparent, very soft and easily scratched with your fingernail

Halite

Rock salt.

Hematite

Black and shiny, dark gray and dull, or rusty red, almost always cool to the touch. Streak- red.

Hornblende

Black with short stubby crystals, and usually striated lengthwise. Vitreous.

Kaolinite

Looks like chalk. No cleavage. White-gray to yellow-brown.

Lepidolite

Pink or lilac color, has darker purple dots, type of mica. Vitreous. Flaky.

Magnetite

A lot like hematite, except magnetic. Gray or black streak.

Malachite

Always green, with a green streak.

Muscovite

White, yellow, or tan mica. Thin and platy.

Olivine

Light green or yellowish-green.

Opal

white and opaque with a greasy or waxy luster. Iridescent.

Pyrite

Fool's gold, often found in cubic or hexagonal crystals, blackish green streak.

Quartz [Agate/Onyx]

Grey, black or brown and is banded.

Quartz [Amethyst]

Purple and transparent.

Quartz [Chalcedony]

Waxy, transparent grey.

Quartz [Citrine]

Yellow or orange and transparent.

Quartz [Crystal]

Colorless and transparent.

Quartz [Jasper]

Orange or red and opaque.

Quartz [Milky]

Crystalline but white or light tan.

Quartz [Rose]

Pale pink.

Rhodonite

All shades of pink and red.

Silver

Metallic silver color. Soft. Metallic. Conductive.

Sodalite

Always blue, but usually a very dark, mottled blue. Colorless streak.

Sphalerite

Almost any color, but usually yellowish, tan, or reddish, resinous luster.

Staurolite

Brown. Almost always forms short, prismatic crystals, can form cruciform twins.

Sulfur

Always some shade of yellow.

Talc

Light green, white, or grey and feels very waxy. Softest.

Topaz

Extremely variable color, but usually comes in well-formed prismatic crystals.

Tourmaline Group

Extremely variable when it comes to color, but it often comes in long prismatic crystals with vertical striations on its surface.

Tremolite

Usually comes in small, bladed crystals, light-colored and sometimes transparent. Asbestos.

Ulexite

Almost always white, and looks like a densely-packed bundle of white threads, opaque in one direction, and conducts light in the other. "TV rock."

Gneiss

Metamorphic, light and dark bands or stripes.

Marble

A non-foliated metamorphic rock composed of recrystallized carbonate minerals, most commonly calcite or dolomite. Looks similar to Granite.

Phyllite

Striped or banded, contains mostly Slate and Mica.

Quartzite

A hard, non-foliated metamorphic rock which was originally pure quartz sandstone.

Schist [Garnet]

Dark rock which has small purple-red crystals embedded in its surface.

Schist [Mica]

Dark flaky rock with Mica flakes.

Slate

Black rock used for chalk boards, derived from Shale.