The Horrors of Glass Filled Rubies

I do periodically write about this issue as I am not convinced that – even though the practice has been around for a while – it is yet common knowledge. In short, glass filling is the practice of fracture-filling rubies with lead glass to improve their appearance. I’m going to lay it on the line, folks: this is bad. It takes poor quality, fractured material and turns it into pretty looking transparent red. It looks good but it is complete junk. Worse than that, it is no longer a ruby.

What is the treatment?

Rubies before and after treatment (photo courtesy of Accredited Gemologists)

Fracture-filling is not new; emeralds have been fracture-filled with oil for years, and it is a completely accepted treatment. The idea being that you find a filler with the same or similar refractive index as the stone and the appearance of fractures are minimised. With emeralds this is fine, as oil is used, which can be removed if necessary and the stones re-oiled; in addition, the original material is usually reasonable. With rubies, the practice of lead glass filling takes rough that is opaque or near opaque – material that would otherwise be unsaleable – and permanently filling it with lead glass. Poor quality corundum is soaked in acid to remove mineral inclusions leaving a weakened and brittle stone; a stone so weak in fact that you could crumble it to powder with your hands. These skeletons are then infused with lead glass, which makes the stone stronger and prettier. The results are actually extraordinary: opaque corundum can be turned into stones with high transparency. So what’s the problem?

The Problems with Glass Filling

Glass-filled ruby damaged during jewelry repair (photo courtesy of American Gemological Laboratory)

There are three main problems: firstly it is an extremely unstable treatment, secondly – and rather crucially – once a ruby has been glass filled it is no longer a ruby and thirdly, it is frequently not disclosed. Let’s take these one by one:

  1. The GIA reports describe glass filled rubies like this: ‘ A manufactured product consisting of lead glass and ruby…unstable to high temperatures and to chemical agents.’ This says it all. The treatment is extremely unstable. Heat during jewelry making or repair will ruin it. Pickle to remove fire-scale will ruin it. Even the wearer can ruin it – most household cleaners will ruin it. Lemon juice will ruin it.
  2. The stones are not rubies. They are ruby and glass composites and in many cases will be more glass than ruby.
  3. The treatment is not disclosed. Sometimes this is blatant fraud; sellers will blatantly charge ruby price for something that is effectively worthless. I have suppliers who say they are finding glass filled rough in with the decent stuff. But most of the time it’s happening because people simply don’t know. They go to a show and buy a ruby and think, ‘oh I got a great deal’ and then sell the stone in jewellery as ruby. Sometimes even the big stores are selling these items undisclosed and, since I’m sure these stores don’t want to wreck their reputations, it must be that they simply don’t know what they are selling. From my own experience, I myself have found at gem fairs that when I’ve asked, ‘is this glass filled?’ that sellers have readily told me. But I have not been convinced that they would have done so, had I not asked.

This is really important, because the retailer is completely liable, whether the mistake is deliberate or accidental, they can be sued for not disclosing this treatment.

How is it detected?

Well, the good news is that unlike other nefarious treatments, this one is really easy to spot under magnification. A microscope or even a loupe will show up low relief fractures, gas bubbles (as is really common with glass), voids, and a yellow and blue flash effect. Failing this, one of the easiest ways – in my experience from attending gem fairs – is simply looking at the price: if it looks too good to be true, it probably is. That is, if you are looking at near-transparent ruby for a few dollars a carat, it’s probably glass-filled. This is fine if you’re buying at this stage – the danger comes if someone thinks they’ve got a great deal, and sell the stone on as ruby.

What’s the take-home message?

I’m not pulling punches with this because it really is complete rubbish. If you buy it and sell it on you are liable. There are also reports that it is being seen in sapphire as well as ruby, although the ruby composites are completely ubiquitous. Always, always ask, if you are buying a ruby. First question: ‘is it glass filled?’ In my experience, you will be told. Carry a loupe and learn how to use it. It’s not even always deliberate fraud; sometimes the sellers themselves don’t know what they’ve got on their hands. And remember, forewarned is forearmed.

joopygems.com

In Praise of Inclusions: Feathers and Fractures 1

  • Joopy Gems Rainbow Moonstone 6mm Rose Cut Round AA Grade, $22
  • Joopy Gems Aquamarine Pear Cabochon
  • Joopy Gems Labradorite Cabochon 6x8mm Oval
  • Joopy Gems Emerald Cabochon 4mm Round
  • Joopy Gems Tourmaline Rose Cut Freeform, 0.39 carats

What a lovely sounding title. If there is one thing that people generally want to avoid in gemstones, it’s a fracture or a feather; whether the crack is surface reaching or completely included in the stone, there’s always the danger of it opening up and splitting or at least weakening the stone. More than that, it’s unlikely that it’s ever going to actively add to a stone’s beauty. However, it’s such a common feature of stones, and indeed sometimes an integral part of the stone’s make-up that it bears closer inspection. A fracture can tell you how the stone was formed, give you information about whether and how it’s been treated

The first thing to be said is that all fractures are not equal. There is a difference between a large, unsightly feather right under the table of a diamond and a delicate fingerprint pattern inside a ruby. In addition, some types of stone are much more likely than others to be fractured in the first place. Let’s find out where they come from and in what forms you might find them.

Where do they come from?

  • During crystal growth; a result of internal tensions caused by structural defects or tectonic activity
  • During crystal growth; an integral part of the stone’s make up – eg parting in labradorite, cleavage etc
  • Whilst formed crystals are in the host rock, due to changes of pressure or mechanical damage produced by tectonic activity.
  • Secondary deposits, when gems are transported and accumulated, eg after being tumbled and washed down a stream.
  • In primary deposits, during mining or the recovery process (blasting and crushing of the rock).
  • During cutting itself: sawing, cutting and polishing, accidental blows or if internal tensions release, or if the stone becomes too hot.
  • In some treatments, due to thermal shock
  • During heating, included crystals inside the host crystal can expand leading to ‘halo fractures’
  •  For mechanical reasons during jewelry making or repair process, eg setting
  • Once in jewellery, normal wear and tear, for example accidental bumps and abrasions
Labradorite with lamellar twinning lines (photo courtesy of Gem Rock Auctions)

Large fractures in stone varieties known for easy cleavage; tanzanite, kyanite or topaz for example should be avoided. They don’t look good and worse, will seriously impact the durability of the stone. Any blow or accidental damage could cause the fracture to open up. As stone-cutter Meg Berry states, she likes to apply the ‘rule of thumb’ when it comes to fractures in stones; namely, if you can snap it with your thumb, you probably ought to. Smaller fractures are a different matter; some milky aquamarine is full of fractures and beautiful, watermelon tourmaline tends to come up quite fractured and of course with emerald it’s almost impossible to avoid. Below, the aquamarine is crazed with tiny fractures, but it adds to the density of the colour and the movement of the cut. The tourmaline slice is imperfect but the colours are still bright and the emerald looks like a planet, with its visible fractures and liquid inclusions.

It’s hard to think of any situation where a large inclusion adds to the beauty of a stone but as I was writing this I thought, if there’s one thing I’ve learned in 10 years in this business and that is that people are endlessly creative and can conjure beauty from the most unprepossessing of raw materials. Enter Jamie Johnson, and her Golden Joinery collection. These are all one of a kind; broken stones set in sterling silver with the seams of both cracked halves dipped in 22k gold. They are absolutely stunning. Below from left Aussie Boulder Opal Joinery Ring, $2860, Golden Joinery Turquoise Earrings, $2330 (photos courtesy of New Twist), Pendant necklace in oxidized sterling silver with 22k gold and rainbow moonstone, $2,970 and finally the group at the bottom featuring turquoise, ruby, boulder opal and green tourmaline (photos courtesy of David Wentworth at Flutter Studios). Aren’t these amazing?

Parting

Ah yes, labradorite. Think of labradorite and in your mind’s eye you’ll no doubt think of a multi-veined stone with the characteristic flash. Years ago I was having trouble with customers sending back stones because not only is the stone soft, but there’s a thing called lamellar twinning. Also known as ‘repeated’ or ‘multiple’ twinning, this results in the layered make up of the stone, which makes it prone to fracturing along these twin planes. It is also, however this make-up which gives rise to the flash – it is the light refracting off these planes that results in the characteristic labradorescence. So when customers tell me they want great flash and no fractures, I kind of want to throw my hands in the air and shriek!! However, I have now done my best with it; not entirely fracture-free but my labradorite is less fractured than most. I try to buy the translucent material with the superior flash, and that way I have happier customers and fewer returns. Even so, you’ll see in the picture below that there are still fracture lines across the stones. It’s pretty much unavoidable.

Cleavage

Cleavage is the tendancy of a crystal to break along distinct planes, and some stones are more prone than others, depending on their specific characteristics. It’s where the atomic bonds are weaker, so the crystal can split easily along those lines. Some have no cleavage – eg quartz, opal, agate, turquoise, ruby and sapphire, and some have perfect cleavage along one or more planes, for example topaz, diamond, kyanite, and all feldspars. It’s more of an issue during cutting – and in fact it used to be used to divide large gem crystals. Now cutters make sure that they cut such stones to minimise the chance of the stone cleaving during setting.

So we have seen that fractures have a function and a place. They may even be beautiful, and certainly they are sometimes unavoidable. I think I ‘ve gone on enough so next time we will be looking at other kinds of fracture – eg halos and fingerprints and also clarity types: the tendancy of some stones to be more included than others.

joopygems.com

A Bluer Shade of Pale

Aquamarine is a really great choice of stone; it’s pretty gemmy without being insanely expensive, it cuts well and takes a really high polish. In its transparent form, it’s more pricey but I just love the milky variety; in lovely shades of pale blue to sea-green, it is misty, hazy and dreamy. It’s common to find this material full of fractures and veils, but when it comes clean with a lovely translucency it is a beautiful, glowing stone. It is named after seawater itself: aqua = water and marina = of the sea and it is in fact a form of beryl, the same mineral as emerald. Unlike emerald, it grows in large and frequently clean crystals so it’s relatively easy to find it in large sizes and in fact can be exceptionally clean. Top colour is a moderately strong blue to greenish-blue. It’s a great jewellery stone and versatile as it’s also exceptionally hard – so a good option for a ring stone. The gemstone for March, aquamarine is offer protection in battle and make the wearer unconquerable; what more could you want! Clockwise from left below: CJ Bijoux aquamarine and 18k gold ring, AF Thomas aquamarine, blue topaz and 18k white gold ring, Gemory Design aquamarine and sterling silver ring and Gems Berry aquamarine and sterling silver ring

We sell a variety of really gorgeous, translucent aquamarine in cabochons and rose cuts as well as rose cut freeforms. To check them out, click here

joopygems.com

When Prehnite Packs a Punch

This slideshow requires JavaScript.

Many years ago, shortly after I started out, the price of prehnite went shooting up. It was one of those odd things, where I had to do a bit of a double take. What could be going on? I was told, it was because it was being used as a jade substitute for the Chinese market. I did another double take, because I just couldn’t see it. Prehnite is so commonly pale, fractured, full of wisps and veils that I just couldn’t see how it could possibly substitute for jade. And then they brought out the good stuff; deep green, clean and glowing with an unearthly, dreamlike lustre. Ever since, I’ve tried to stock the better stuff, because when prehnite is good, it’s very, very good indeed. You might never even have heard of it. The GIA thinks not, as they have included it in their ‘Hot Gemstones’ round-up, but that makes it an excellent choice as you are not likely to run into it in your local jewellers. It’s a bit different, unusual and the prices (except for the really fine stuff) are pretty sensible. For meaning, it is best known as the stone of unconditional love, said to connect the head to the heart. It’s found mainly in Australia, Canada, China and the USA, and it’s a good choice for anyone who likes their stones untreated as it never is.

Pictured below are a couple of really gorgeous specimens: top is marmarModern’s Prehnite and Sterling Silver Ring – I just love this setting which manages to be interesting and unusual and not detract at all from the beauty of the stone. Below that is Mastergoldcraft’s Prehnite and 14k Rose Gold Ring ; a study in elegant simplicity.

marmarModern Prehnite and Sterling Silver Ring, $130
marmarModern Prehnite and Sterling Silver Ring, $130

Mastergoldcraft Prehnite and 14k Rose Gold Ring, $875
Mastergoldcraft Prehnite and 14k Rose Gold Ring, $875

I’ve just taken delivery of some beautiful quality 6mm rose cuts, lovely saturated green colour, clean quality, $3.75 per stone.  You can view them by clicking here. To shop all prehnite, click here.

joopygems.com