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Rocks of the Sixteen to One Mine


Many different rocks and minerals can be found in the Sixteen to One Mine, however the most significant are: Tightner schist, serpentine, mariposite, and vein quartz.


· Tightner schist is a hard metamorphic rock that ranges in color from dark gray to light brown. This rock unit represents a thick accumulation of mud and silt in a deep ocean basin.


· Serpentine, a dark gray to gray green rock is an alteration product of peridotite (core/mantle material) that has been forced up deep seated faults associated with the boundary of the oceanic plate with the continental plate (Plate Tectonics). Serpentine contains up to 10% magnetite, 10% chromite and ½ % nickel. Since peridotite contains more gold (up to 20 ppb) than serpentine (up to 10 ppb) this is believed to be the source of gold in Alleghany quartz veins.


· Vein quartz, a pure white rock, has been deposited within open spaces along reverse faults. Metamorphism of the Tightner schist and serpentinization of peridotite are probably the source of the quartz.


· Mariposite gets its name from the green colored mineral mariposite which is a chrome-rich mica mineral, a variety of sericite. Mariposite is the product of alteration of serpentine by gold bearing solutions rich in CO2. Over 90% of the rock mariposite is calcium, magnesium, iron carbonate.


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