Radiolarian Chert
Biogenous sedimentary rock.
Radiolarian chert of Jurassic age, Franciscan Formation. Radiolarians are single-celled aquatic animals that have a spherical amoeba-like body with a spiny skeleton of silica. Their skeletons can accumulate as a slimy ooze deposit on the seabed. Chert forms from siliceous ooze that accumulates very slowly in the deep ocean basins in cold water, far from shore. The red is iron-oxide and other metal impurities, probably from dust and possibly traces of meteor ash. Red chert is also called jasper. It's natural hard nature (composed of microcrystalline quartz) makes it idea for cutting and polishing as a semi-precious stone.
San Benito River gravel bar near Hollister, CA. |
| https://gotbooks.miracosta.edu/rocks/sedimentary/5.html |
2/2/2021 |
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