Organic

Mineral Composition: primarily carbon

Features: Black, dull to shiny, typically soft, burns

Coal

Clastic

Mineral Composition: Gravel (chert, quartz, arkosic)

Features: Looks like a big clump of multiple minerals

Conglomerate

Organic

Mineral Composition: calcite, CaCO₃

Features: Hard, dense, conchodial fracture, reacts with HCl (acid)

Limestone

Chemical

Mineral Composition: CaCO₄ 

Features: Can be scratched by a fingernail, no reaction with HCl (acid)

Rock Gypsum

Chemical

Mineral Composition: Microcrystalline Quartz, SiO₂

Features: Hard, conchodial fracture, no reaction with HCl (acid)

Chert

Clastic

Mineral Composition: sediment, sand, Quartz

Quartz Sandstone

Clastic

Mineral Composition: Abundent feldspar grains

Arkosic Conglomerate

Clastic

Mineral Compostion: Mud, silt, clay

Features: Thin sheets

Shale