Limestone (fossiliferous or weathered)

Sedimentary carbonate rock primarily composed of calcium carbonate (CaCO3)

Hardness of 3 on the Mohs scale, color ranges from yellowish-brown, tan, to gray, luster is earthy to dull, crystal structure is microcrystalline or cryptocrystalline (calcite), cleavage is rhombohedral in pure calcite crystals but generally absent in massive rock form, specific gravity around 2.7.