This tunnel was driven in the 1860s by miners in search of commercial-quality coal. Two hundred feet of the 400-foot tunnel are open for exploration.
Black Diamond Mine - Prospect Tunnel
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By kjfitz @ 2008-07-06 19:49:24
Anonymous
@ 2021-03-14 14:52:04
Can you find rose crystal quartz at Contra Loma Hiking Trails?