Opal

Info: This amorphic mineral have no internal crystal structure. It have the same chemical formula as quartz, but it is softer and lighter than him. It is fragile mineral with typical dissolving of the light on the freshly cutted surface, reflecting various colours. When exposed to air it loses his water and shine with it. The colour of the opal divides several sub-minerals of the mineral: the bluish or redish colouration is typical for the precious opal, fiery opal reflects light in strong yellow and red colours, the common white opals hydrofane and hyalite have white reflection. Opal is found near gazers.

How to recognize: In UV-light opal flourescent in yellow or green colour. When heated it losses water untill it dissolves to quartz.

Found: The precious opals were found in Transylvania and in USA, black opal is typically found only in Australia, fiery opal is found in Mexico. World-wide famous deposits of opal were found in Slovakian Dubnik.