. 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. slides/Interesting Mineral Sample 8_9_07.html Fri, 18 Jul 2008 20:37:16 -0700 JAlbum 8.0 Claremont Chert at the Pacifica site, Oakland, CA on Aug. 9, 2007. Picture taken by Robert S. 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)." Claremont Chert at the Pacifica site, Oakland, CA on Aug. 9, 2007. Picture taken by Robert S. 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)." slides/Interesting Mineral Sample 8_9_07.jpg slides/Churt-MG30.html Fri, 18 Jul 2008 20:37:16 -0700 JAlbum 8.0 Claremont chert formation on Claremont Avenue, Oakland, CA on March 11, 2004, by Marilyn Goldhaber. Claremont chert formation on Claremont Avenue, Oakland, CA on March 11, 2004, by Marilyn Goldhaber. slides/Churt-MG30.jpg