Color in Hand Sample Calcite and dolomite are colorless, so limestone or dolostone with no impurities should be white. Trace amounts of clay may color the rock tan or light gray. Trace amounts of carbonaceous material will color the rock dark gray or black, and hematite will color the rock red. Do not try to use color to distinguish micrite, sparite, and dolostone . Abundant microfossils, mainly forams, in micrite matrix.
White color is due to absence of carbonaceous matter.
0.6mm Microfossils are forams and fragments. Irregularly-shaped patches of coarse sparite are cavity fillings in micrite. Black color is probably due to micron-sized carbonaceous matter or clay. Notice the sparry overgrowth on rounded core with dusty margin ,that maintains optical continuity with crystal making up the plate. Areas occupied by clean calcite represent initial porosity in bioclastic sediment.