Opal from Virgin Valley, Humboldt County, Nevada USA

A large precious opal limb cast after wood, from Virgin Valley, Nevada, USA. This is a solid piece of opal taking the shape of a piece of wood that had previously rotted away and left a void for the opal to fill in volcanic ash layers altered to a bentonite/montmorillonite clay, some clay is still adhering in a few places. Due to the tendency of most Virgin Valley Opal to crack or craze upon drying or exposure to atmospheric conditions, it is kept in a water filled display dome to preserve it as a specimen. Measured about 4x3x3 inches. Shown wet in my hand.