Minerals in Sediments
Chemical Sediments
Outline
Organic or biogenic sedimentary rocks are rocks that owe their existence to biological processes. They may be clastic accumulations of animal skeletons debris (many limestone), biologically catalysed precipitates (some ironstones), accumulations of plant detritus (coal) or alteration products of siliceous organisms (chert).
| TEXTURE | COMPOSITION | ROCK NAME |
|---|---|---|
| Clastic | Clastic shell fragments. | COQUINA (limestone) |
| Clastic | Microscopic shells of coccoliths | CHALK |
| Altered | Microscopic siliceous organisms, recrystallized silica. | CHERT |
| Clastic | Consolidated plant remains. | COAL |
The table lists a few examples of organic (biogenic) sedimentary rocks. Significant deposits of nitrates and phosphates.
Minerals in Sediments
Chemical Sediments
Outline