Rocks & Minerals

Rocks, minerals, and geology in the north hills and Claremont Canyon watershed. This album will grow only as pictures with full identifications are submitted by viewers.

$Interesting chert sample at Pacifica transmitter site, Oakland, CA on Aug. 9, 2007. Photo by Bob Nelson. Comments by Doris Sloan, emerita Prof. of Geology at UC Berkeley: "An excellent and interesting example of the weathering of rock. The brown coating is iron oxide. It is the result of fluid rich in dissolved iron migrating through the fractures in bedrock (that is, rock in place in the ground), and leaching into the rock. Sometimes when you see this, it looks like the iron dissolved out of the piece of rock itself and leached out to the edge. But in this one, it looks to me as if the iron was picked up in other rocks, dissolved in water that then flowed through the chert (or whatever the rock is)."$

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