serpentine - teaching hand specimen from the Melones fault zone
Serpentine is a mineral formed by the metamorphism and igneous activity associated with subduction zones, where an oceanic plate is diving below a continent. It is derived from the metamorphism of magnesium-rich peridotite from the mantle. It's the state "rock" of California. Its chemical formula is Mg6(Si4O10)(OH)8
Serpentine's structure is sheets of silica tetrahedrons sandwiching layers of magnesium hydroxide. The magnesium hydroxide layers imperfectly stack with the silica tetrahedron sheets, causing bending of the layers. In most serpentines, these layers form convoluted sheets, well represented in these examples. When the sheets bend into tubes, fibers of asbestos are formed.
These textbook specimens were collected from the Melones fault zone in the American River Canyon, Placer County, California, right in the Forty-Niner gold belt. They are glossy dark green and say "squeezed" to a student.
The specimen with a black pen and two coins in the photo has slickensides, fault striations, on one side.
Too heavy for First Class, these will ship in a Regional Priority Mail package for $10.28 or less, depending on your zip code, and can be combined with other items.
Select a specimen: You can select a specimen by telling us what is in the photo with it, a black mechanical pencil, black and silver pen or one of those plus some number of coins, or you can let us make the selection.
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