Sandstones with Carbonate Cement 64X
Most sandstones contain some kind of mineral material in the pore spaces that binds the grains together. This is called a mineral cement. Sandstones occasionally have carbonate mineral cements that cause the rock to react to HCl. Carbonate-cemented sandstones may have any of the sedimentary structures seen in other kinds of sandstone. Two kinds of carbonate cement are common in Carboniferous coal fields:
- (64X CaCO3) Calcite-cemented sandstone
- (64X FeCO3) Siderite-cemented sandstone
Both varieties are generally harder than typical gray sandstones, which they resemble. Calcite-cemented sandstones may have a bluish tinge to the gray color and may have some mottling. They will effervesce (fizz) readily with dilute hydrochloric acid. Siderite-cemented sandstones generally have a pink or red hue compared to gray varieties, and will only effervesce when a powder is created by scratching the specimen.
Once the variety of cement is determined, proceed to the Bedding page to further classify the specimen.