GEOL 1020 Lecture Notes - Lecture 2: Cryptocrystalline, Sodium Chloride, Gypsum
7 Sep 2016
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Rounded or semi-rounded (implies they traveled a long way) Deposited along a stream channel or shoreline. Angular (implies they haven"t moved from their source) Quartz sandstones (rounded, well-sorted, light), graywackes/immature sandstones (angular, several different grains), arkoses (feldspar grains) Silt-sized particles finer than sand, coarser than clay. Many colors: black, gray, brown, red, gray (depending on organic materials/iron oxides) Accumulation of clay at the bottom of oceans or lakes. Difficult to identify because it can take many different forms. Made of mineral calcite (caco3), so bubbles when hydrochloric acid is applied. Many different forms (coquina, fossiliferrous, lithographic, chalk, encrinal, travertine) Originally starts out as limestone, but chemically altered by replacing some of its calcium with magnesium. Bubbles when hydrochloric acid is applied, but slower than limestone. Soft and can be scratched or bruised easily. Not salty, won"t bubble with hydrochloric acid. White or pale reddish-brown (when stained by iron oxide) Can be baked and ground into plaster of paris.
