Rock Identification Exam

Quartz Sandstone

Visible sand, Grains are clear to milky

Marble

Large Reflective Cleavage Planes, Reacts to Acid

Rhyolite

Dull Pink or Beige, No visible Grains

Quartzite

Sand Grains w/o spaces, red or green or white, scratches glass, will not react to acid

Scoria

Red to black, Lots of holes (vesicular)

Arkose Sandstone

Visible sand, Quartz + some pink feldspar grains

Schist

Flattened but not flat, visible mica flakes, shiny

Granite

Large Interlocking Grains, light with Black Minerals, reflecting Chunks

Shale

Splits into thin flat plates, fragile

Micritic Limestone

No visible grains, smooth, won’t scratch glass, reacts to acid

Gneiss

White Matrix with Black Stripes

Conglomerate

Large Rounded Grains, No Acid Reaction

Obsidian

Black, Occasionally red, conchoidal Fracture, glassy texture

Slate

Splits into thin plates, durable

Basalt

Dull Black, fine grained, no mark on paper

Diorite

Large interlocking grains, half black, half white

Coal

Black, Blocky, Marks Paper

Fossiliferous Limestone

Gravel-sized Fossils, Reacts to acid

Gabbro

Large interlocking grains, mostly black, reflective chunks

Chert

No visible grains, smooth, hard, No acid Reaction

Andesite Porphyry

Dull green or gray, large darker crystals, “Chocolate chip cookie”

Oolitic Limestone

Sand-sized balls, reacts to acid