ZIRCON

December Birthstone

Zircon (the name derives from the Persian zargun meaning golden-coloured) is a mineral belonging to the group of nesosilicates, its chemical name; zirconium silicate.

The natural colour of zircon varies between colourless, yellow-golden, red, brown, blue and green. Colourless specimens that show gem quality are a popular substitute for diamond and are also known as "Matura diamond". In geological settings, the development of pink, red and purple zircon occurs after hundreds of millions of years annealed in geological conditions above the temperature 350 degrees Centigrade.

The crystal structure of zircon is tetragonal crystal system. It is a common accessory to most granite and felsic igneous rocks. Due to its hardness, durability and chemical inertness, zircon persists in sedimentary deposits and is a common constitute of most sands.

Australia leads the world in zircon mining, producing 37% of the world total and accounting for 40% world EDR (Economic Demonstrated Resources) for the mineral. Zircon has played an important role during the evolution of radiometric dating. Because zircons can survive many geological processes, they contain a rich and varied record.

Currently zircons are typically dated by uranium-lead (U-Pb) along with other techniques. They contain trace amounts of uranium and zircons from Jack Hills in Western Australia have yielded U-Pb ages up to 4.404 billion years, interpreted to be the age of crystallization, making them the oldest minerals so far dated on Earth.