Dunham's classification, shown above, requires that one first decide if primary texture is preserved. If not, then the rock is called crystalline. If primary texture is preserved, the next question is whether the components are organically bound: if so, then the rock is a boundstone. If not, then one inspects the rock for carbonate mud (micrite of Folk). If there is no mud, the rock is grainstone. If mud is present, the relative abundance of mud versus larger grains determined whether the rock is a mudstone, wackestone, or packstone.
In the following list of examples click the thumbnails to open a larger view of the image. Image windows can be re-sized or scrolled, depending on your preferences and the capabilities of your computer monitor.
Mudstone
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Mudstones are mud-supported, and contain less than 10% grains. |
Wackestone
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Wackestones are mud-supported, and contain more than 10% grains by volume. |
Packstone
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Packstones are grain-supported, but still contain mud. |
Grainstone
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Grainstones are grain-supported, but do not contain mud. |
Boundstone
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Boundstones have a recognizeable depositional texture, where the original components are bound during deposition. |
Crystalline Carbonate
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Crystalline carbonates do not have a recognizeable depositional texture. The subdivisions are based on texture or diagenesis. |