Disthene

Disthene is abundant in the Realms, and is easily cleaved, but difficult to cut in facets without unintended splitting. It usually has many inclusions. Disthene is found in crystals ranging in color from dark blue to pale green; fine blue facet-grade crystals are the most prized at double the base value. Disthene is also known as kyanite. A typical stone has a base value of 10gp.