Mariposite

Mariposite – also sometimes called “emerald quartz” – is a chromium-rich variety of mica in white dolomite.  It was first found near Mariposa, California, where it formed when islands off the coast collided with North America, creating California.  It can also be found in Newfoundland, Canada, where it is called virginite, and in Europe.

Mariposite is a type of marble, formed in a skarn.  Skarns are common places for gemstones to be found, as they are an unusual geological setting, where silica-rich magma is injected into calcium-rich limestone.  The magma reacts with the limestone to form various types of rocks with combinations of silica, calcium and various metals that are in the magma.  Gold and silver are commonly found in mariposite.

The minerals in mariposite include mica, calcite or dolomite, and quartz.  These minerals all have very different hardnesses with mica at 2.5, calcite at 3, and quartz at 7.  It is important to keep this in mind when polishing, as they will polish at different rates and with different lusters.  This stone makes stunning polished material, however.