I collected this specimen in 2009 at a roadcut outcrop along the Shoreline Highway, a few kilometers southeast of Stinson Beach, California.  My wife and I were driving north from San Francisco to visit Point Reyes National Seashore, with its earthquake-trail walk that celebrates the observations of G. K. Gilbert following the Great 1906 Earthquake.

Age & Formation
Serpentinite from fault zone along San Andreas fault, California.