Juergen Freund / Andamooka opals held in hand, South Australia, June 2011

Juergen Freund / Andamooka opals in boxes, South Australia

Juergen Freund / Andamooka opal field with a deep open pit, South Australia

Graham Eaton / Pebbles of semi-precious Jasper, Quartz SiO2, in shingle on a beach, Aberdaron, Wales. The jasper is present in the rocks associated with an ancient plate boundary. July

John Cancalosi / Cross section of Agate stone, Silicon dioxide, Mexico

Adrian Davies / Amethyst crystal

John Cancalosi / Detail of a slice of blue Agate, Cryptocrystaline quartz, Brazil

John Cancalosi / Crazy lace agates, cryptocrystaline quartz, Chihuahua, Mexico

Larry Michael / Semi-precious stones and glass for sale at Zion NP, Springdale, Utah, USA

Larry Michael / Semi-precious stones and glass for sale at Zion NP, Springdale, Utah, USA

Larry Michael / Semi-precious stones and glass for sale at Zion NP, Springdale, Utah, USA

Dr. Axel Gebauer / Jewellery, semi-precious stones and corals for sale at market, with a prayer wheel. Yushu, Qinghai Province, Tibet, China