Made a reservation for six for a Saturday tour at 3 PM; there were about 14 people on our tour. Guide was knowledgeable, tour about 25 minutes or so, additional time for tasting/sampling beers and ales. Also a gift shop to browse in. Tours are free, you can donate to a local charity if you wish.
Tiburon is an incorporated town in Marin County, California. It is located on the Tiburon Peninsula, which reaches south into the San Francisco Bay. The smaller city of Belvedere (formerly a separate island) occupies the south-west part of the peninsula and is contiguous with Tiburon.
Metamorphic Rocks of Ring Mountain, Tiburon. At only 602 feet in elevation, Ring Mountain is hardly a mountain. But it is well known to geologist and biologist alike because of its unusual geology and the unique plants that grow in the serpentine soils on the Tiburon peninsula. Serpentine is a metamorphic rock: a rock changed by heat and pressure. The high concentration of magnesium and calcium in the soils is usually toxic to plants, but some rare plants thrive [see: http://www.marin.cc.ca.us/~jim/ring/rplant.html].