Snowflake obsidian

Snowflake Obsidian is a variety of obsidian found in the Realms in large deposits (of volcanic origin). It is black with grayish, flower-like patches that often, especially if some stone can be cut away, radiate symmetrically, resembling snowflakes. It is brittle and weak, but often used for small carvings. It is either tumbled to gemstone form for sale, or sold in "trade blocks" (large, irregular chunks, as quarried) of up to twenty five pounds (twelve kilograms). A typical specimen has a base value of 10gp.