Apophyllite is a hydrated potassium calcium silicate mineral with a tetragonal crystal system and a hardness of 5. It is most commonly colourless, white or gray. There are also rarer specimens in varying shades of green. Apophyllite often appears in cubic or pyramidal shapes. Most specimens on the market are from India, especially the Poona and Nasik districts. Apophyllites are also found in Italy, Germany, Canada, Iceland, Greenland and Brazil.