is a Calcium Sulfate with formula CaSO4 and hardness of 3.5.
The common massive type is called Angelite, but here we mean the anhydrite that forms nice prismatic crystals in general of blue color,sometimes occur also in colorless, and yellow. Its structure is fibrous with many parallel crystals needles that are a problem for the cutter! In fact it may split along the C axis quite easily. From Mexico.
Size: 13.5x12x9.5 mm.