B. May or may not be scratched with a knife; fairly uniformly fine grained 1) Soft; feels slippery or soapy when wet; may disintegrate in water; gives off an earthy odor when breathed upon Clay 2) Loose; gritty; particles smaller than table salt Silt 3) Solid rock; often in thin beds or sheets; separates into silt; mica flakes may be present; may contain fossils; may effervesce slightly Siltstone 4) Solid rock; breaks into thin platy sheets; may feel slippery when wet; black to gray; may contain fossils; shows thin laminations; may effervesce Shale ([10]) 5) Solid rock: does not break into thin platy fragments; may effervesce slightly Mudstone 6) Solid rock; usually gray or black; splits into platy sheets or slabs; harder than shale Slate 7) Powdery; white or light brown; commonly associated with chert and quartz from which it forms Tripoli ([19])
III ORGANIC ROCKS (DARK COLORED)
A. Soft; spongy when wet; very lightweight when dry; forms in swampy places 1) Fine mass with coarse plant fragments; dark gray to black Peat ([13]) 2) Plant fragments small and not easily recognized; fine-grained; black to dark gray; earthy Muck B. Hard but can be scratched with a knife 1) Black; contains bands of shiny and dull material; burns well Coal ([14]) 2) Dark gray to black; does not contain shiny bands; splits into thin sheets; burns poorly or not at all Bituminous shale
EQUIPMENT FOR COLLECTING
1. Hammer (bricklayer’s) with one chisel or pick head.
2. Cold chisel about 6 inches long with an edge about ½-inch wide.
3. Dilute hydrochloric (muriatic) acid (10 percent solution) in a dropper bottle for testing the presence of carbonate minerals. Mark the bottle POISON. If acid is spilled on skin or clothing, wipe immediately and, if possible, rinse with water.
4. Magnifying glass or hand lens—10 power is probably most useful.
5. Hardness testers—penny, square of window glass, pocket knife, or nail.
6. Streak plate—piece of unglazed white porcelain (such as the back of a tile) for testing the color of the streak of minerals.