SAMPLE
Scratch with a knife and apply dilute acid (HCl)
If rock does not scratch, go directly to I, II, or III
No effervescence or very slight effervescence
I Coarse-grained (p. 37)
II Fine-grained (p. 38)
III Organic (p. 39)
Slight effervescence
gray, light gray, white, or brown: Dolomite
Vigorous effervescence
Composed of pebbles that effervesce
Rounded pebbles: Limestone conglomerate
Angular pebbles: Limestone breccia
Composed of crystals of calcite, fossil shells, or oolites:
Limestone
Composed of banded layers of crystalline calcite; commonly found in
caves, forming stalactites and stalagmites: Travertine
Large amount of insoluble residue left on acid-treated surface
Individual grains seen with unaided eye: Calcareous sandstone
Individual grains not seen with unaided eye: Calcareous shale
Composed of porous or cellular mass of calcite; commonly found near
springs and waterfalls: Tufa