Chrysocolla: Gemstones Information

Chrysocolla: Gemstones Information

Chrysocolla has the composition (Cu,Al)2H2Si2O5(OH)4nH2O and can be found as translucent to opaque blue to blue-green acicular crystals of the orthorhombic system though ornamental varieties are crypto-crystalline.The texture can resemble enamel. The hardness is 2–4 and the SG 1.93–2.4.Specimens are notably brittle. Sources differ on RI values but for practical purposes an RI of around 1.5 will be obtained on the refractometer.Specimens can show considerable colour variation with oxides of copper,iron and manganese included with the green. Chrysocolla is often found in a matrix of quartz, in which case the constants may be those of quartz.Chrysocolla is a mineral of secondary origin occurring in the oxidized zones of copper deposits where it may be mixed with malachite or turquoise. Occurrences are widespread but most ornamental chrysocolla comes from the south-western US or from Israel where ‘Eilat stone’ is found near Eilat in the Gulf of Aqaba. Much of the chrysocolla of jewellery consists of very attractive cabochons of green or blue chrysocolla impregnating either rock crystal or opal.