This is the serpentinite ashtray (serpentinite gabbro). Dimensions: 4.1 x 4.0 x 1.0″ (10.3 x 10.2 x 2.6cm). Weight – 25.6oz (726 grams). Origin: Russia, Ural.
Some information about serpentinite:
Serpentinite is a rock composed of one or more serpentine group minerals, the name originating from the similarity of the texture of the rock to that of the skin of a snake. Minerals in this group are formed by serpentinization, a hydration and metamorphic transformation of ultramafic rock from the Earth’s mantle. The mineral alteration is particularly important at the sea floor at tectonic plate boundaries.
Serpentinization is a geological low-temperature metamorphic process involving heat and water in which low-silica mafic and ultramafic rocks are oxidized and hydrolyzed with water into serpentinite.
In Russia serpentinite deposits are found in the Ural Mountains.