Hi Howy,
It's good to know that others are starting on the same journey of learning about gemstones that I started some time back. I hope that you had a look at the links that I summarized in a recent post on the TGX thread. Coloured gems are actually quite an interesting thing to look into. Here are some of the more important basics for beginners:
- the 4 C's for coloured gem valuation -- colour is most important factor, followed by clarity, carat size, and cut
- there are variations in clarity and carat size ranges between coloured gemstones leading to different valuation standards; for example, emeralds almost always have a lot of inclusions, rubies far more so than sapphires, and both rubies and emeralds almost never exceed about 5-10 carats for the largest stones -- as a result, a near perfect, large sapphire is far less valuable for the same size stone as an emerald or ruby
- if you compare coloured gemstones to diamonds, on average they are much less brilliant, although rubies and some emeralds can glow brilliantly due to the scattering of light caused by chromium (TGX emeralds, like the Columbian ones, have chromium)
- the majority of gemstones have historically come from south Asian and SE Africa from alluvial deposits
- much like Indian diamonds were long since exhausted, most ruby and sapphire deposits from Thailand, Kashmir, Cambodia, Vietnam, and even Sri Lanka have been exhausted or near exhausted (especially the higher quality ones); Madagascar is one of the few places where there have been discoveries in recent years and the better of these stones are passed off as Burmese or Sri Lankan stones
- today, almost all rubies and sapphires are enhanced, particularly through heat treatment; this can significantly improve the colour and clarity of the stones, and those stones that are lucky enough to look good without enhancement are rare and command a large premium -- note that TGX's Baffin Island sapphires are naturally blue without heat treatment |
