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.

Calcite-cemented sandstone (64X CaCO3) in core.
Siderite-cemented sandstone (64X FeCO3) in core.

Once the variety of cement is determined, proceed to the Bedding page to further classify the specimen.

 

 

Last Modified on 2017-06-30
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