Jewellery, Watches and Objects of Vertu

A green zircon dress ring, the oval mixed-cut metamict green zircon in simple eight claw setting, mounted in yellow precious metal, shank stamped ‘9ct’, zircon approximately 11.5 carats, ring size N. £1000-1500

The stone has had a verbal report from the Gem Certification Services Laboratory, December 2015, confirming the stone is a natural metamict zircon.

The term Metamict refers to a mineral that has become virtually amorphous due to the breakdown of the original crystal structure by internal bombardment by alpha particles (helium nuclei). Green metamict zircons are almost exclusively Sri Lankan in origin and are Precambian in age, meaning they are over 800 million years old.

Metamict zircons display a lower refractive index and lower density, than ‘high’ zircons. The metamict destruction of zircon can result in angular tension fissures, which delineate the former tetragonal crystal structure. Strong magnification reveals the angular shapes to be systems of much smaller fissures oriented parallel to each other and at right angles. These fissures are the result of expansion during isotropization and are therefore typical of the green low zircons of Sri Lanka, as are fine parallel lines from unequal itropization, both of which are visible in this stone under magnification. See The Photoatlas of Inclusions in Gemstones, by E.J. Gubelin and J.I.Koivula, Opinio Verlag Basel, 2004.