Gemstones are a mystery. They have fascinated man for thousands of years and we have attributed supernatural powers and values to coloured gemstones that – perhaps – don’t always stand up to scientific scrutiny! But these brilliant coloured gems continue to intrigue us and with improved technology, more variations and even new gemstones are being discovered such as Muscravite, a very rare black gem mineral recently found in South Australia.
The colour in a gemstone is caused by a combination of the crystal structure and the way in which it absorbs light, and the chemical elements within the mineral. A skilled gemmologist will identify each gemstone by examining the crystal structure, the hardness, specific gravity and optical properties. When tested, some gems show a very narrow band of colour – peridot, for example, the distinctive yellowish-green colour caused by iron. Sapphires and Tourmalines have wide bands of colour from blue to pink, yellow, purple and green and also parti-coloured stones. Some gems, when cut en cabochon – polished into a smooth dome shape – show flashes of white in the form of a star or cats eye.
The colour, and in particular the inclusions in coloured gemstones, also indicate its origins. The most desirable emeralds – those that display the distinctive green fire – come from Columbia and it is possible for the experienced gemmologist to even identify the mine by close examination and identification of the inclusions.
Coloured gemstones are valued by their weight, the excellence of the cut, rarity, the vivid colour and durability of the mineral. Today, both coloured gemstones and diamonds have come to the attention of investors hoping for a quick profit. But be warned! This is not a field for those who are not qualified gemmologists; so buy your gemstones, set them in some fine jewellery and enjoy wearing them, leaving the investors to worry about the future values.
Image: Photography by Paul Hartley, Hartley Studios: www.hartleystudios.com. Aquamarine, tanzanite and ruby rings with diamonds; all from the Diamonds for Today Collection. Published by kind permission of IDJC. For further information, contact firstname.lastname@example.org