Gemmology is the study of gemstones and gemstones are represented as a specific sub set of minerals and rocks that are usually processed by lapidary methods into gemstones that possess three characteristics of beauty, rarity and durability. As most gemstones are used in the jewellery industry, there is a link here to a need to determine the characteristics that separate one gemstone from another. Not all red gemstones are rubies for example. More recently as manufacturing and industrial processes have developed their is a need for the modern gemmologist to be able to determine the difference between a “natural” gemstone and a “man-made” gemstone.

You can learn more about gemmology and how to study gemstones by visiting the Gemmological Association of Australia’s website:

http://www.gem.org.au/education/courses/courses_outlines/

The purpose of gemmology remains to achieve a complete distinction between the “natural” gemstone, the “synthetic” or “artificial” or “man-manufactured” (sometimes incorrectly termed ‘created’) gemstone, or further the artificially “treated” gemstone (sometimes incorrectly termed ‘enhanced’). You might ask why does it matter? The simple answer is that most consumers prefer a “natural gemstone” or one that has “come out of the ground (mined) as distinct from a “synthetic” gemstone (one that has come out of the factory. Natural gemstones will inevitably be preferred by most consumers and so they will place a higher value on the natural material.

There have been some recent discussions on the international scene as to whether a gemstone should be called a “natural gemstone” or more simply a “Mined Gemstone” however this is another discussion. The modern gemmologist should not lose sight of being able to tell the difference!

Opal gemmology follows the normal procedures of non-destructive gemmological testing. These procedures examine the observable qualities of gemstones which include the physical or mineralogical properties of opal and more particularly measurable observations of Refractive Index (RI), Specific Gravity (SG) (sometimes known as and related to density), examination under exposure of excitation Ultraviolet light, and Microscopic examinations of opal characteristics such as imperfections and inclusions. Advanced material science methods of examinations for gemmological purposes is also beginning to become a necessity for the modern gemmologist, and these will be discussed in the section on “opal Science”.

IMITATION and ‘SYNTHETIC’ or TREATED GEMSTONES

A synthetic gemstone is a gemstone made by man in a factory (or perhaps an industrial Laboratory). The gemmological definition of a synthetic gemstone is ‘a gemstone that has the same physical and chemical properties of it’s natural counterpart’ (amended).

An imitation gemstone is “ by definition a gemstone that ‘looks like’ but does not necessarily have the same physical and chemical properties as it’s natural counterpart’ (amended).

A treated gemstone is a gemstone to which some form of “change” has been applied. Te change of the gemstone is most usually an industrial or laboritory process that has been applied to a gemstone

This can cause a little bit of consternation as there is much literature talking about synthetic opals in gemmological literature. Also a discussion on imitation opals must inherently include a discussion on both natural imitations (other gemstones that look like opal) and synthetic or artificial materials that have been man-made to look like opals.

Lets start with the “so-called” synthetic opals.

In about 1973 both the Australian CSIRO (Commonwealth Scientific and Industrial Research Organisation) and the French industrialist Pierre Gilson began investigating the manufacture of precious opal. (you can read about this in the “Sciences” section of the Library). It is debatable who produced the first “synthetic opal” (you can read about this in Opal History). However it is certain that Pierre Gilson manufactured the first commercially available “synthetic opals”, and these were used in the manufacture of jewellery items. (much detail regarding Synthetic Opals are available in back issues of “The Australian Gemmologist”, as the subject has been covered extensively over many years).