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RMSH 4/2008 Diamonds VOLUME 43, NO. 4 A PRIL 2008 DIAMONDS AND D IAMOND S IMULANTS MEETING Wednesday This month’s topic was originally “Jewelry.” However, this April 23, 2008 topic is virtually impossible to write a short 3-4 page article 7:00—9:00 pm about. Therefore we have a little compromise. This Makiki District month’s emphasis will be on Diamonds, and Diamond Park simulants. “Diamonds ” Diamonds are just about the last complish, but it also became radioac- industry where one can purchase a tive in the process (some of them are NEXT MONTH natural gemstone with confidence. still radioactive). In 1942 stones Wednesday Granted there are treatments and were greened more than superficially May 28, 2008 enhancements, however these are over days in a Michigan cyclotron “Tourquoise” usually explicitly prohibited. There without becoming radioactive for are specialists in fancy (natural) color more than a few hours afterward, LAPIDARY diamonds who will not buy or sell thus a stage was set to color dia- stones known to have been irradi- monds in a safe, fast, permanent Classes on ated, although these stones have way. By coupling irradiation and Thursday been marketed for more than 50 heating, research gemologists began Evenings years. As a result, irradiated dia- producing green, blue, yellow, brown 7:00—9:00 pm monds are pretty much segregated and black diamonds on a commercial from the mainstream and are sold scale in the early 1950s. exclusively by a tiny number of dealer-devotees. MEMBERSHIP This is ironic because dia- COSTS monds were the first gem to be col- 2008 orized in the lab with radiation. In 1904, British scientist Sir William Single: $10.00 Crookes proved that Diamonds Family: $15.00 could have their color changed by burying small stones in radium bro- mide salts. Crookes’ methods succeeded, however it left something to be de- sired since diamonds turned green on the surface only. Furthermore not only did it take months to ac- YAG - Yttrium Aluminium Garnet Rock and Mineral Society of Hawai‛i INC. Diamonds, page 2 The irradiation process pro- low in diamonds is caused by nitro- . duces just about every diamond hue gen.” found in nature, however it does so Anyhow, the nearly identical with varying degrees of success. color of natural and irradiated yellow Natural and treated golden diamonds makes a good case for the brownish-yellow stones (possessing a latter, especially after factoring in the color that dealers call “burnt or- enormous price differences between ange”) can’t be told apart merely by the two. As result of this, the Deep- sight. dene is the largest irradiated Dia- In 1992, some unscrupulous mond in existence. dealers took to submitting borderline The majority of commercially “fancy-intense” stones to GIA which available synthetic diamonds are yel- High concentrated 2 they gambled would eke out that low in color and produced by so inch Er-YAG crystal grade. Those that did had been called High Pressure High Tempera- zapped to deepen color and heighten ture (HPHT) processes. The yellow value, then offered for sale as top- color is caused by nitrogen impuri- notch all-natural yellows. Luckily, ties. Other colors may also be repro- labs caught their artificial coloring. duced such as blue, green or pink Recent scams involving undisclosed which are a result of the addition of irradiation of yellow and also green boron or from irradiation after syn- diamonds recall the most famous thesis. diamond scandal of modern times In the case of synthetic dia- involving a mammoth natural yellow monds, for example, depending on stone called the “Deepdene,” whose the method of production (either color was deepened several shades high-pressure/high-temperature by irradiation without disclosure of [HPHT] or chemical vapor deposi- this fact. In 1971, this 104.52-carat tion [CVD] ) and the color of the stone was sold by Christie’s Geneva diamond (colored, D-Z color range for about $1.2 million. Although the or D-J color range), several methods stone’s color was pedigreed of natu- of identification can be attempted by ral origin, spectroscopic examination a gemologist or gemlab. CVD dia- showed a telltale 5940 absorption monds can usually be identified by line—proof of irradiation since its an orange fluorescence, D-J colored discovery by GIA’s Robert Crown- diamonds can be screened through ingshield in 1956. the Swiss Gemological Organiza- Why did the stone’s con- tion's (SSEF) Diamond Spotter, and signor fail to reveal the treatment? stones in the D-Z color range can be “At the time,” Crowningshield ex- examined through the DiamondSure plained, “many believed that color in UV/visible spectrometer which is a diamonds was due to radiation. So tool developed by De Beers. are not YAG-Co single crys- putting stones in a cyclotron, it was seen in synthetic diamonds. tal argued, did what nature would have done anyway. Today, we know yel- Rock and Mineral Society of Hawai‛i INC. Diamonds, page 3 High Pressure High Tem- thought to be a wholly artificial ma- perature Treatment (HPHT) was terial, until 1982 when its natural first used to turn yellowish diamonds counterpart—discovered in Siberia into fancy colored diamonds, now it and named Tausonite. Tausonite is also used to transform some un- remains an extremely rare mineral in popular brownish diamonds into nature, occurring as very tiny crys- more expensive colorless diamonds. tals. Its most important application Some companies claim HPHT isn't a has been in its synthesized form treatment at all, calling it a technique wherein it is occasionally encoun- that finishes the job nature started. tered as a diamond simulant. That attitude, and the fact that the process is difficult to detect, has The name tausonite was Strontium Titanate made HPHT a controversial topic. given in honour of Lev Vladimi- (Fabulite) rovich Tauson (1917-1989), a Rus- Gemological Institute of sian geochemist. Disused trade America (GIA) grading reports now names for the synthetic product in- indicate when HTPT treatments are clude strontium mesotitanate, Fabu- detected by stating "HPHT An- lite, Diagem, and Marvelite. nealed" or "Artificially Irradiated" in the Origins portion of a report. Synthetics are usually trans- Only diamonds that are laser- parent and colourless, but can be inscribed with the words "HPHT doped with certain rare earth or tran- PROCESSED," "IRRADIATED," sition metals to give reds, yellows, or under a specific registered name browns, and blues. Natural tausonite are graded. is usually translucent to opaque, in shades of reddish brown, dark red, A Diamond simulant is defined as a or grey. Both have an adamantine non-diamond material that is used to (diamond-like) luster. Strontium ti- simulate the appearance of a dia- tanate is considered extremely brittle. mond. Diamond-simulant gems are often referred to as diamante. Yttrium Aluminum Garnet (YAG), a modern diamond stimu- The distinction between a lant, discovered in 1828 by Friedrich synthetic diamond (man-made dia- Wohler. It was used as an alternative mond consisting of carbon atoms to Sapphire as an optical material arranged in the typical diamond Yttrium aluminium garnet (YAG, structure) and a diamond simulant Y3Al 5O12 ) is a synthetic crystaline (not a carbon compound with the material of the garnet group. YAG diamond structure) is very important. is commonly used as a host material Some of the Diamond Simulants are: in various solid state lasers. How- ever, YAG for a period was used in Strontium Titanate is an oxide of jewelry as a diamond and other gem- Strontium and Titanium. It was long stone stimulant Rock and Mineral Society of Hawai‛i INC. Diamonds, page 4 Colored variants and their doping diamond. elements include: green (Chromium), blue (Cobalt), red (Manganese), yel- Moissanite is a new product, but its low (Titanium), purple origins go back to 1893 when Dr. (Neodymium), pink, and orange. As Henri Moissan, a French chemist faceted gems they are valued (as syn- and later a Nobel Prize winner, iden- thetics) for their clarity, durability, tified minute quantities of natural high refractive index and dispersion. silicon carbide, known as Lusenite, in the Diablo Canyon meteorite found As a synthetic gemstone, in a remote area of Arizona. Re- YAG has numerous varietal and cently, these elements were repli- trade names : alexite, amamite, circo- cated in a synthetic material to pro- lite, dia-bud, diamite, diamogem, dia- duce a synthetic gemstone with simi- monair, diamone, diamonique, dia- lar properties to diamond. The gem- monite, diamonte, di'yag, geminair, stone is more brilliant than diamond, gemonair, kimberly, Linde simulated Refractive Index 2.65-2.69, has a diamond, nier-gem, regalair, replique, higher lustre than diamond at 20.4%, somerset, triamond, YAIG, and yt- and a hardness of 9.25, diamond be- trium garnet. ing 10. Relative Density: 3.21. Moissanite replicates a diamond so Cubic zirconia (or CZ), the cubic well, that it could be sold as a dia- crystalline form of ziconium dioxide, mond to the unwary buyer. is a mineral that is widely synthesized for Moissanite is most convinc- use as a diamond simulant. The syn- ing as a diamond substitute in small thesized material is hard, optically sizes. Larger stones still show slight flawless and usually colorless, but greenish or grayish tones that are may be made in a variety of different difficult to eliminate. Careful exami- colors. It should not be confused nation through the crown facets (not with zircon, which is a zirconium through the table, since that's ori- silicate. Cubic zirconia is extremely ented on the optic axis) under a rare in nature. loupe or microscope should easily Because of its low cost, durability, reveal facet doubling caused by dou- and close visual likeness to diamond, ble refraction, as well as very non- synthetic cubic zirconia has remained diamondlike surface polish and inclu- the most gemologically and eco- sions.
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