Firstly, thanks to everyone for the overwhelming response we received for last week’s Orange Sapphire Update. We will be clarifying some of the issues raised in this week’s Ask The Gem Guy.

Following your lead, this week we thought we’d bring you a strictly educational Gem Scoop, answering the many questions we receive on how to use Gem Tools.

While most standard gem tools are easy to use (see Tools Of The Trade below), some are a little more complicated and, as two-time Gem Quiz Winner and amateur gem enthusiast Ralph De Martino recently discovered, with some gem tools there is more than one way to use them:

“On the subject of identifying Spinels. I was reading some past Gem Scoops and saw that a quick way to tell them apart from Ruby is with a Dichroscope. I just received one and it shows that Ruby has red and orange-red color spectrums while Spinel only shows one color in all axes.”

The Dichroscope is an often over looked tool, and as well as verifying authenticity, it can also help less experienced cutters orientate facets by showing how the colors of a piece of Rough Gem will look when finished. An inexpensive Gem Tool, Dichroscopes are handy for:
 

	Telling what the true colors are on each axis and what they actually look like separately.
	Orientating for axis and color.
	Getting a good idea of what the colors will look like when mixed in a cut stone.
	A good quick identification when purchasing Rough (i.e. a piece of Spinel is far less expensive than a piece of Ruby and as they are often found in the same area it is not uncommon for them to be mixed together).

A Dichroscope consists of Calcite and a lens in a short tube with a small square aperture at the other end. The Dichroscope separates the polarized rays so that they may be observed side by side. To use your Dichroscope, simply direct light onto your gem and look at it through the Dichroscope while slowly turning the gem. As you view the gem in all directions, look for different colors or shades of color. This is useful in distinguishing: Blue Sapphire from Blue Spinel; Ruby from Garnet or Spinel; Emerald from Demantoid or Tsavorite Garnet; any doubly refractive gemstone (e.g. Amethyst) from glass.

Ralph also found an interesting way to tell Noble Red Spinel from Ruby just using your eye and a Flashlight:
 

“You hold a faceted gem close to your eye with its table almost touching your cornea. You shine the flashlight through the gem and into your eye and look for a rainbow spectrum off one of the facets. If the spectrum shows red, green and blue it’s a Spinel. If it’s only red and blue, it’s a Ruby.”

Simon Bruce Lockhart F.G.A., D.G.A., E.G. (a.k.a. the Gem Guy) comments on this practical method of “kitchen sink gemology”: “Sometimes called the distant vision technique; as well as Ralph’s interesting discovery regarding spectrums, you can also use this method to estimate R.I., Double Refraction and basic spectral properties. He may have missed these as he was possibly placing the gem too close to his cornea. Ideally, the gem should be about 2 cm below or to the side of your eye at an oblique angle.” Well done Ralph and it just goes to show that with curiosity, passion (and a few simple Gem Tools) you too can discover the fascinating world of gemstones.
 

Ralph has also been experimenting with another traditional gem-tool: “I did some more research and it seems that both the Synthetic Dark Blue and Natural Cobalt Blue Spinel will show red under a Chelsea Filter.” Correct again Ralph!

Developed in 1934 by the Gem Testing Laboratory of the London Chamber of Commerce and the Chelsea College of Science & Technology, the Chelsea Filter was designed to distinguish Emeralds from Simulants. The Chelsea Filter is a combination of two gelatin filters that transmit only deep red and yellow/green light. As Emeralds transmit light in the deep red spectrum but absorb light in the yellow/green spectrum, this combination is the most practical. To use the Chelsea Filter, place your green (or blue) gems under a strong electric light (but not fluorescent tubes) ensuring the gems receive as much light as possible. If you hold the Chelsea Filter close to your eye you should see the following results:
 

Natural Emeralds will appear pinkish-red since Emerald absorbs the yellow/green light; Synthetic Emeralds will show a more intense red; Emerald Simulants will appear green, as will Synthetic Green Spinel, Peridot, Green Sapphire and Green Tourmaline. However Chrome Green Tourmaline will appear red or pink.

Demantoid Garnet and Green Zircon will appear similar to Emerald but with a negative reading on the refractometer (the scale will appear uniformly dark since no total internal reflection occurs). Aquamarine, Blue Topaz and Zircon will appear green. Lapis Lazuli will show a weak brownish-red while Cobalt Glass (once very common in costume jewelry) shows a deep red.

Natural Blue Spinel appears red, as does Synthetic Dark Blue Spinel and Natural Cobalt Blue Spinel. However, Synthetic Light Blue Spinel will show pink-orange. Blue Sapphire will appear very dark green (almost black) with the exception of Blue-Purple Color Change Sapphire, which usually appears red.

The Chelsea Filter can also be used to separate Natural Green Jadeite from color enhanced Jadeite. Most treated Jade will appear reddish while Natural Jade will appear green.

Of course today, electronic Gem Testers have become very popular, especially for comparing Diamonds with Moissanite, Cubic Zirconia, White Sapphire and other Simulants. Diamond Testers check a gemstone’s thermal conductivity, as this is much higher in Diamond than any of its pretenders. One advantage of electronic testers is that they can be used on both mounted and un-mounted gemstones. A high rate of heat transference indicates that the gem being tested is a Diamond while a low rate of heat transference indicates that the gem is probably not. This is easily communicated by either green/red flashing lights or a simple beep. One Word Of Caution: When using Diamond Testers make sure the Diamond is at room temperature, if it has been warmed by the wearer’s body temperature it may give an inaccurate reading.
 

Spend time in a gem market anywhere in the world and you’ll soon see the basic three tools that every gem-trader carries: Loupes, Tweezers and a Flashlight. Whether these are neatly combined in a Kit or Case or simply carried in the pocket, they are definitely universal.

The standard Loupe provides 10x magnification and is essential for inspecting the facets, tables and inclusions of a gem. Although harder to use, 20x loupes can help you identify synthetic flux gems. As there are many different brands and varieties of Loupes available (prices range from $4.99 to $75.99), go for what you can afford. Sometimes you’ll also see gem-traders wearing an Optivisor. Often used by Gem-carvers and traders in Rough Gems, these space-age-looking devices are very convenient when you’re dealing with piles of gems or when you need to keep your hands free, but they only provide magnification of 2 to 4 times.

In order to hold gems firmly, Tweezers are an essential Gem Tool and again, a wide variety are available, including those with a non-slip coating. Often a little tricky for the beginner, an easy way to avoid shooting the gem across the room (an expensive exercise if you’re purchasing gems in an open air market) is to first turn the gem onto its table facet, using the tweezers to firmly but gently grasp the girdle. Simon (a.k.a. the Gem Guy) prefers Lockable Tweezers as they afford him a secure grip at all times, which is especially handy for safely passing a stone to a colleague or when used in combination with other diagnostic Gem Tools (e.g. Dichroscopes, Chelsea Filters, Microscopes etc.). Ideal for the novice gem-inspector, another easy to use alternative are 4 and 5 clawed Grabbers.

A combination of natural sunlight and the bright beam of a Flashlight is the best way to examine all optical characteristics of a gem, including: Refraction; Transparency; Luster; and Sheen (i.e. Chatoyancy, Asterism, Opalescence, Schiller, Play of Color and Fluorescence). They are also the quickest way to determine the degree of change found in Color-Change Gems. Small but powerful, pinpoint Flashlights are the most useful.

Other very common Gem Tools include Shovels or Scoops, for scooping up piles of loose gemstones; Polishing Cloths and Solutions to ensure that your Gems and Jewelry really sparkle; Digital Scales for measuring carat weight; and Gauges for measuring gem size in millimeters.

All of the Gem Tools mentioned above (and many more) are available at Thaigem.com. Remember, if you ever have any questions regarding the use of any of our Gem Tools, please don’t hesitate to Ask The Gem Guy:gemguy@thaigem.com

Click here to see our entire range of over 400 gem types.

Got a question about gems? Every week our Gemological Manager, Simon Bruce Lockhart F.G.A., D.G.A., E.G. (a.k.a. the Gem Guy), answers one of the more popular questions asked about gems and gemology.

Before Simon answers this week’s question, thanks to the reader who wrote in questioning last week’s erroneous comment that the dispersion of Zircon is higher than Diamond. Of course it isn’t! Simon’s got no excuse, but in-between a madcap buying trip to India and the pressure to get the Gem Scoop out on time, this slip-up just slipped through.

Q. Would you please explain diffusion treatment in Sapphires? I understand it is a heat treatment but would like more information. Is it just a surface treatment or is the color change throughout the gemstone?

A. The Dictionary of Science, published by the Oxford University Press, defines diffusion as “the process by which different substances mix as a result of the random motions of their component atoms, molecules and ions. In solids, diffusion occurs very slowly at normal temperatures.”

In the Corundum industry there are two enhancement-processes that use the word diffusion, “surface diffusion” and the new “bulk diffusion process”, also known as E(IM) (Enhanced by Inducing Internal Migration and Formation of Color Centers). Other than the word “diffusion”, the two processes have little in common and this unfortunately seems to be causing many misconceptions about the differences between the two processes.

What is surface diffusion and how does it work? Surface diffusion relies on external metallic coloring elements being diffused onto the surface of the gem. Compared to the E(IM) method, it produces highly consistent results. Generally cheap, pale or colorless corundum is used as a “blank canvas”, upon which specifically desired colors can be diffused or “painted”.

Natural corundum is Aluminum Oxide (Al2O3) colored by metallic elements (i.e. Fe, Ti, Cr, etc.). Surface diffusion is achieved by coating these “blank canvases” with Aluminum Oxides and the appropriate coloring agents (i.e. Iron and Titanium for Blue Sapphire, Chromium for Ruby, Titanium for Star Sapphire etc.). The gems are then subjected to very high temperatures over a prolonged period of time.

The depth of surface diffusion penetration is very small (a fraction of a millimeter), and after enhancement the gems need to be re-polished to remove the damage left by the partial melting of the gem’s surface. After re-polishing, this very thin layer of color is often unevenly distributed. Facet junctions tend to be darker due to diffused color penetrating from both sides of the junction. The coloring can also bleed into surface-reaching fractures and inclusions, which then appear as patches of intense coloration.
 

Surface Diffused Gems are very convincing imitators of Natural Ruby and Sapphire. As they very often contain natural inclusions that can fool the unwary, I strongly recommend that both jewelers and gemologists keep at least one reference sample in their collections for comparison with natural gemstones.

What is E(IM) (a.k.a. Bulk Diffusion) and how does it work? In E(IM) it is believed that “color centers” are the chromophoric catalysts (i.e. the cause of color). As stated last week, the migration theory suggests that beryllium catalysts flush through the Sapphire knocking magnesium atoms out of place. Like billiard balls, beryllium acts like a cue ball to knock magnesium balls away from their original positions forming “color centers”.

So what are the key differences between E(IM) and surface diffusion? In the E(IM) method, the new colors produced are reliant on each gem’s inherent chemistry. Significantly, identical or similar colored Sapphires simultaneously subjected to E(IM) enhancement display numerous color variations. In fact, leading scientists and gemologists have been surprised by the variety of colors this method produces.

By comparison, surface diffusion does not rely on a gem’s inherent natural chemistry. With controlled quantities and mixtures of coloring agents, surface diffusion has highly predictable and consistent results.

As individual colors produced by the E(IM) method have their own occurrence rates (or for want of another word, rarity), this has led many to conclude that the value of these gems should be higher than those enhanced by surface diffusion. Unlike surface diffused gems, some E(IM) enhanced gems can be recut without any loss of color. Unlike the coloring found in surface diffused gems, the color distribution in E(IM) gems is deeper and more varied.
 

	A 2.10 Carat Oval Cut E(IM) Sapphire. The gem was chosen for its very notable inclusions underneath the table facet			The gem is now recut into a 1.51 Carat modified Emerald Cut. Note the presence of the same inclusions. The stone has retained exactly the same color hues.			The gem cut in half and submersed in Di-iodemethane. As the coloration penetrates to the core, this gem could be recut without any loss of color.

Got a question about gems? Ask the Gem Guy gemguy@thaigem.net.

Create Your Jewelry allows you to select Gems and Diamonds from our enormous online inventory. Match them with jewelry designs from our huge online gallery (or submit your own) and we then custom make the jewelry of your dreams to your exact specifications.

This week’s profile is an 18 Karat White Gold Ring set with a 3.4 Carat Tourmaline and twelve 6-point Accent Diamonds. Total Price: US$475.42. Handcrafted and shipped in just 9 days from receipt of order this is design number RGG000200M in the Create Your Jewelry Design Gallery.

Congratulations to Bryan Campbell of Kansas for winning a 2 Carat Peridot in the latest Gem Quiz. As one of the easiest Gem Quizzes yet (the answer was actually in the Gem Scoop of August 2), we had a flood of responses! Thanks to all entrants and congratulations to the lucky winner!

Q. In Ancient Times, what made Peridot mining a dangerous occupation?

A. Pit Vipers.

Click here to view all the Gem Quiz questions and winners.

Thaigem.com gives you the chance to win FREE gems with the Gem Quiz. The current prize is a 2 Carat Spinel. To win this gorgeous gem, simply answer the following:

Up until the 16th Century, what was red Spinel known as?

Send your answer to gemquiz@thaigem.net by August 27, 2002. The winner will be selected randomly from all correct answers. Gem Quiz winners will be informed via email and also announced in the Gem Scoop. All decisions are final.

Thanks for taking the time to read about the colorful world of gems and recent developments at Thaigem.com.

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