Corundum

Info: The crystals of corundum have a different shapes. In clear form corundum is colourless, but when mixed with other elements it becomes with different colours. The colour divides the corundum to several sub-mineral varieties: the not-transparent and mudy common corundum, the red ruby, the blue saphire, the orange yellow padparacha, and smirek, the mixing of corundum with oxides of the iron. Typical for corundum is the optical effect named asterismus - light, reflecting from the mineral is in the form of little stars.

How to recognize: Corundum is the only mineral with hardness 9, it can be scratched only by diamond.

Found: Great crystals were found in Uralls (Russia), Canada, USA and Madagascar. The most valluable precious gems were found in Barma, Thailand, Kambodia, Sri Lanca, Australia and Montana (USA). In Czech Republic corundum was found in some pegmatites in Pokojovice, Písecko and in Hvožďan. Beatiful saphires were found in river Jizerka.

Used for: The saphire and the ruby varietes of corundum are famous precious gemstones and are used in jeweliry. Today ruby and saphire can be made sintheticaly.