"AP physics"

Clear rhombs showing double refraction.

A cleanup crew of consumers and decomposers will help keep habitats balanced and bio-active.

Lustrous, black 'hard coal'.

Glassy; most specimens float in water.

Coarse-grained, with microcline, biotite and horblende phenocrysts.

Shiny black volcanic glass showing conchoidal fracture and some spherulites.

A cleanup crew of consumers and decomposers will help keep your habitate balanced and bio-active.