If like me however you prefer natural gemstones and would like some basic tips and information to help decide what's real and what isn't (before and after you buy), read on MacDuff...
I bought a gem refractometer a while back and now test all my stones. I'd definitely recommend one for anyone remotely serious about buying gem stones. They cost from about £50. With a bit of practice, as long as a gem has a flat polished surface you can get an RI reading (refractive index = how much the mineral bends light which passes into it) which is pretty specific to most of the common gem minerals. By the way, I don't sell refractometers. Or Gemstones.From my own personal ebay gem buying experience, I'd estimate around 50% of gems sold as 'natural' are ...not. This figure might be higher for international sellers, especially in the Far East. Surprisingly, in the UK, the most prolific offenders appear to be the 'professional' ebay sellers. Amateurs might be excused for just repeating the information they were given by their original seller, and for selling gems without testing them, but the professionals should (and I suspect do) know better.
"It says 'Natural Stone' in the advert, so it must be real." Right? -Nope. Ebay does not actively vet adverts. They wait for complaints, so it's up to you to find out. Several of the largest UK ebay gem sellers sold me glass and synthetics as 'natural stones' until I got the refractometer and realised. Actually they still sell me fakes, but now I know what I'm getting, and can ask for a refund with confidence.
Some sellers offer certificates with their fakes. The certificates are worthless, generated by the seller, and usually only the photo, size and weight are relevant to the stone they come with. Buyers obviously like them, but they don't seem to think about why a professional seller would list a 'natural ruby' with a Buy-it-Now price of under £12 and an accompanying 'appraisal certificate' which values the gem at £933! I'm not kidding, -that is a listing current at the time of writing. The ruby might well be natural and genuine (dyed massive corundum anyway), but the valuation on the certificate is pure fantasy.
A few definitions might be helpful here:
Gemstone: a catch-all term for anything gem-like. Even 'real gemstone' should be ignored, as it could apply just as well to to a cubic zirconia, a glass cabochon, or a natural diamond.
Sim/simulated/simulant: purely a look-alike, and not the same composition as the natural mineral. eg: sim rubies could be CZ, glass, or anything else, but not corundum. If you suspect you have a glass pretender, and have other gems to compare it with, try the tongue test: don't warm the stone with your hand, but touch the tip of your tongue to it. Paste or glass will feel warmer than CZ, and quartz, sapphire, zircon and diamond will feel progressively colder. This is due to their differing thermal conductivity. Some diamond and gem testers (eg the Presidium) work on the same principal. One seller sold me a London Blue Topaz, but it felt far too warm to the tongue. My refractometer also tests for birefraction, a property of most mineral types including topaz. The blue 'topaz' had no birefraction, and turned out to be glass.
Treated: this should mean a natural stone which has been treated, eg: heated, irradiated, oiled, dyed etc, to enhance it. Many gems are listed as untreated, when in fact they are, but treatment in itself should not be seen as a fault. Some treatments reverse themselves over time or when exposed to light though. Heated and irradiated Kunzite reverts back to it's original greyish colours if exposed to sunlight. Often though, sellers will hide the true origin of a stone here: if you see 'hydrothermal' listed as a treatment, it usually means the stone is a manufactured hydrothermal crystal, often quartz.
Hydrothermal quartz: this is manufactured quartz crystal made by dissolving ground pure quartz in water at very high temperature and pressure and recrystalizing it on plates in a cooler part of the vessel. Don't try this at home. Dye elements are added to make almost any colour. MANY of the 'natural' amethysts (blue, green and purple), citrines, smokeys and ametrines sold on ebay are hydrothermal quartz wrongly sold on as 'natural' because they are made from quartz. They share the same properties as natural quartz too, so it can be hard to tell the difference by testing. Hydrothermals are usually simply too perfect in clarity, too even in colour (and too cheap!). They may also contain spherical bubbles or tiny breadcrumb-like seed crystal inclusions, so a 10x magnifier or loupe is great for closer examination. Natural stones often have inclusions too though and, more rarely, some have bubbles. Any cheap, large IF (internally flawless) flat-colour quartz gem on ebay is most likely to be hydrothermal quartz. Not just quartzes though- I recently bought a large 'Natural Brazilian Santa Maria aquamarine' which turned out to be hydrothermal quartz.
Synthetic/Lab stones: these are crystals grown or fused from the same basic elements as the natural stones. Includes hydrothermal quartz. Lab sapphires/rubies: should be made from corundum, but often aren't. Lab emeralds should be made from beryl via the hydrothermal or flux methods, but I've been sold 'lab emeralds' by a major seller which were obviously glass. I guess he thought the glass was made in a lab of sorts. Again, the refractometer is invaluable: I recently bought a 'Natural pink Topaz' which tested clearly as synthetic sapphire. The seller who sold this is still selling the same stones (with the same photo!) as 'Natural pink Topaz'. btw, I kept the stone, -fluoresces beautifully under ultraviolet light!
CZ / Cubic Zirconia: A very hard and 'sparkly' cubic crystal often used as a diamond simulant, but can be made in almost any colour. Strictly, I can't use my refractometer to test CZ (or diamonds) as the refractive index is too high. The fact that I don't get a reading though is diagnostic if the stone I bought was sold as something else and I am expecting a reading! I saw a large flawless 'Padparadscha Sapphire' on ebay recently which looked familiar. I found that the photo used on the listing was from another seller's ebay shop, and that shop only sold CZ Padparadscha sapphires which might cost a thousandth of the price of the real thing. I messaged the seller, not mentioning the photo, and asked if it was a Padparadscha sapphire or a CZ Padparadscha sapphire, pointing out that the two are very different. He replied simply: 'It is a Padparadscha sapphire'. Strangely enough, I still didn't bid.
Origin: -take anything listed under origin with a pinch of salt. Sellers know it's better to put something than admit they don't know, so they often choose somewhere mineral-rich like Brazil or Africa. The seller of the Santa Maria aquamarine (hydro quartz) I mentioned earlier said he had a certificate of authenticity from the Brazilian mine. Yeah right, -that's why after he refunded, he said I could keep the stone anyway!
Don't overlook flawed stones. Nature isn't usually perfect. I'm not a jeweller, and I like to see natural flaws. Then again, some sellers list perfect clarity IF hydrothermals stones as VS (small inclusions) just to make buyers think the stones must be natural!
Do all the research you can. Research real and synthetic stones so that you'll know what to look for. Before you bid, check the sellers feedback carefully; often the comments are more useful than the ratings, as buyers are generally very reluctant to post negative feedback whether they've had a refund or not. Look for buyers who test the stones and put the results in the feedback comments.
If, when the gem arrives, you aren't satisfied, ask for a refund. This can be more difficult if you don't have test results to back you up, but keep calm and take your time. Don't immediately post the seller negative feedback, or they'll have nothing to lose. Send a polite but firm message detailing your concerns and give them a chance to put things right. If you know the stone was wrong, you can ask for the P&P to be refunded too, but you need to be sure. If you send it back, get proof of postage at the very least, and keep that safe, as there is currently a rash of 'chargeback' fraud, where someone says they didn't get the goods posted to them and Paypal could recharge the refund you got, up to 180 days later. Don't agree to not post feedback -this is against ebay rules anyway- help other buyers by making the most of your feedback to the buyers. If your stone tested good, then say so. If it proved fake, but the seller gave a refund, you don't have to post negative feedback, but do use that comment line to say what happened.
Keep a record of all your purchases. That way you'll know which sellers to trust.
If you have a bad experience on ebay, report the seller to ebay, and don't just put up with it. Ebay doesn't make it easy to do this because automated consumer service systems cost a lot less than people reading written emails/messages. But it can be done.
Remember, fake stones will continue to be listed until the risk of being caught outweighs the profits. So let's be careful out there.....