This is the cluster of datolite crystals with black ilvaite. Dimensions: 2.0 x 1.6 x 0.9″ (5 x 4 x 2.2cm). Weight – 1.1oz (31 grams). Origin: Russia, Dalnegorsk.
Some information about datolite:
Datolite is a semi rare silicate mineral of the gadolinite group. It appears as surface-growing, short and stubby, prismatic, large crystals. Its crystal structure is monoclinic, as it has two axes of unequal length inclined to each other, with the third lateral axis at a right angle to the plane that contains the other two.
Its aggregates are huge, granular, dense, fibrous, and has porcelaneous crusts. Datolite has a vitreous to greasy luster, blue luminescence, and ranges from transparent to translucent. Colorless, yellow, green, and red crystals have been found. Datolite fuses easily into transparent glass, turning the flame green. It dissolves easily in acids.
It occurs in basic, igneous rocks, in metamorphic rocks, and occasionally in ore veins. Datolite is a secondary mineral in cavities in basalt and serpentinites and hydrothermal deposits, associated with zeolites, prehnite, and calcite.
Datolite is a mineral with a hardness of 5-5.5 on the Mohs scale of mineral hardness. Datolite is named after Greek «datysthai» — to divide. These Monoclinicly structured gems are made of diatomaceous silica, their full chemical compound being Ca(B,OH)SiO4.