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OEC
The '''carbonates''' are [[compounds]] of one or more [[metallic]] [[elements]] or [[semi-metal|semi-metals]] with the [[carbonate]] (CO<sub>3</sub><sup>2-</sup>) radical. One member of this class, [[calcium carbonate]] (CaCO<sub>3</sub>), is sufficiently [[common]] to form large bodies of [[limestone]], a [[sedimentary rock]]. The carbonates are [[brittle]] [[minerals]], and many of them break easily along [[crystal]] directions to develop the characteristic [[rhombohedral]] [[cleavage planes|cleavage]]. A few carbonate minerals are in bright [[color|colors]], but many of them are [[white]], [[colorless]], or [[transparent]]. Chesterman, p. 431
The '''carbonates''' are [[compounds]] of one or more [[metallic]] [[elements]] or [[semi-metal|semi-metals]] with the [[carbonate]] (CO<sub>3</sub><sup>2-</sup>) radical. One member of this class, [[calcium carbonate]] (CaCO<sub>3</sub>), is sufficiently [[common]] to form large bodies of [[limestone]], a [[sedimentary rock]]. The carbonates are [[brittle]] [[minerals]], and many of them break easily along [[crystal]] directions to develop the characteristic [[rhombohedral]] [[cleavage planes|cleavage]]. A few carbonate minerals are in bright [[color|colors]], but many of them are [[white]], [[colorless]], or [[transparent]]. Chesterman, p. 431
==Classification==
An admittedly Old Earth system the "Dunham classification" relies on empirical observation.
The concept of grain support figures heavily in the '''Dunham classification''', which divides carbonate rocks into two broad groups; those whose original components were not bound together during deposition and those whose original components formed in place and consist of intergrowths of skeletal material. The former group is further subdivided as to whether or not the grains are mud-supported or grain supported. The latter group are called ''boundstones''. If the rock consists of less than 10% grains it is called a ''mudstone''. If it is mud supported with greater than 10% grains it is called a ''wackstone''. If the rock is grain supported, it is called a ''packstone'', if the grains have shapes that allow for small amounts of mud to occur in the interstices, and a ''grainstone'' if there is no mud between the grains.
==Sources==
==Sources==