Chemical Sedimentary Rocks
Chemical sedimentary rocks consist of precipitated material that was once in solution. The precipitation of material occurs in two ways: inorganic processes & organic processes (biochemical origin). The appearance of most chemical sedimentary rocks is that of interlocking crystals (May resemble an igneous rock).
| Rock | Sediment | Texture |
Composition | Environment |
|---|---|---|---|---|
| Limestone | Calcite (lime) mud | Varies; fine to coarse | Calcite | Shallow, warm, carbonate-rich waters of the continental shelf |
| Travertine | Calcite (lime) mud | Usually fine grained | Calcite | Hot springs and caverns |
| Chert | Quartz (non-organic in origin) | Very fine grained | Quartz | Replacement mineral due to diagenesis in limestones, etc., or in deep marine sediments. |
| Evaporites: Rock Salt |
Precipitated Salt | Varies; fine to coarse | Halite | Evaporation of seawater enriched in sodium and chloride |
| Evaporites: Rock Gypsum |
Precipitated Gypsum | Varies; fine to coarse | Gypsum | Evaporation of seawater enriched in calcium and sulfate |
| Diatomite | Plankton with silica shells | Very fine grained | Silica (quartz) | Deep sea floor (cold water) |
| Chalk | Plankton with calcite shells | Very fine grained | Calcite | Deep sea floor (warm water) |
| Coquina | Calcite (lime) mud + fossils shells! | Coarse grained | Calcite | Basically a shell hash; near shore tidal areas. |
| Fossiliferous Limestones | Calcite (lime) mud + fossils! | Coarse grained | Calcite | Shallow, warm, carbonate-rich waters of the continental shelf |
| Coal | Altered plant remains | Fine grained | Carbon | Swamps |