Chalcedony

Info: This name is used for the microcrystalical varieties of quartz with soft fibre structure. It can be translucent, but more often is opaque with wax shine. Chalcedony is very hard mineral. His colour may vary between opalic, milky or even blue colour.

How to recognize: When heated or exposed long time on sunlight, most of the chalcedony crystals change their colour from yellow or brown to red and orange.

Found: Large deposits of chalcedony were found in Brazil and Urugway.

Variants: The most famous variant of chalcedony is agate, with whitish, red to brown and yellowish colouration. Onyx is black and white. Translucent variants of chalcedony are the orange carnelian, red to brown sard and the green chryzopras. Also known are the darkgreen chalcedony variants with red dots - heliotropes, and moss agates, which is colourless and translucent chalcedony with green, moss-like growings of amfibole inside the crystal.