This is a terrific sample of rough Sapphire in a matrix, from Zazafotsy Quarry, Ambahatraso, Ihosy, Fianarantosoa, Madagascar.

Sapphire, as you know, is a gemstone, a variety of the mineral corundum, which is an aluminium oxide. It is typically blue in color, as in this case, but natural "fancy" sapphires also occur in yellow, purple, orange, and green colors. The only color which sapphire cannot be is red – as red colored corundum is called ruby, another corundum variety.

A nice addition to an enthusiast's collection!