The Monkey Puzzle Tree: Claimed Source Of Jet

(via Gemmology Queensland, Vol.5, No.6, June 2004)

The araucaria family (Araucariaceae) contains three remarkable genera of cone-bearing trees: Araucaria, Agathis, and Wollemia. They are tall trees native to forested regions of South America and Australia. In majestic size and beauty, they certainly rival the coniferous forests of North America and Eurasia. In fact, they are considered the southern counterpart of our northern pine forests. The type genus Araucaria is derived from ‘Arauco’, a region in central Chile where the Araucani Indians live. This is also the land of the ‘monkey puzzle’ tree (A. araucana), so named because the prickly, tangled branches would be difficult for a monkey to climb. Fossil evidence indicates that ancestral araucaria forests resembling the present day monkey puzzle date back to the age of dinosaurs. In fact, it has been suggested the tree’s armor of dagger-like leaves was designed to discourage enormous South American herbivorous dinosaurs, such as Argentinosaurus weighing and estimated 80 to 100 tons. Another ancient South American species called pino parana or parana pine (A. angustifolia) grows in southern Brazil and Argentina.

Any discussion of fossilized araucariads would be incomplete without mentioning a medieval gemstone called jet. Jet is a semi-precious gem excavated in Europe and formed by metamorphosis and anaerobic fossilization of araucaria wood buried under sediments in ancient seas. Ancestral forests that metamorphosed into jet date back to the Jurassic period, about 160 million years ago. They were similar to present day forests of monkey puzzle trees (Araucaria araucana) that grow in South America. Chemically, jet is hard, carbonized form of bituminous coal with a density similar to anthracite coal. Anthracite can be readily identified by its metallic luster. Jet takes a high polish and has been used for shiny black jewelry for thousands of years. It has a specific gravity of 1.3, almost as hard as the ironwood called lignum vitae (Guaiacum officinale). Jet became very popular during the mid 19th century England during the reign of Queen Victoria, and was often worn to ward off evil spirits and during times of mourning. In the first century AD, the Roman naturalist and writer Pliny described the magical and medicinal attributes of this beautiful mineral. The well-known analogy of ‘jet’ and ‘black’ was coined by William Shakespeare in his ‘black as jet’ from Henry VI part 2. One of the most famous areas for mining of Victorian jet is Whitby on the rugged Northeast coast of England. Although they are similar in hardness, anthracite has a metallic luster and jet is dull black. Jet takes a high polish and has been used in various carved jewelry, such as cameos and intaglios. The Victoria jet broach (circa 1890) was a popular item of jewelry during the 19th century.

Rare Diamond Goes Bright Pink In UV Light

(via Gemmology Queensland, Vol.5, No.7, July 2004/annanova.com 16/1/04)

A potentially unique diamond, which goes vivid pink when exposed to ultraviolet light, has been found in South Africa. The 13.7 carat diamond, being called the Tirisano Easter Diamond, was recovered from the Tirisano Diamond Mine in Ventersdorp diamond district of the Republic of South Africa.

Exposure to (presumably long wave) ultraviolet light causes the diamond to turn vibrant fluorescent pink. It’s not unusual for diamonds to change color in this way, but vivid pink is one of the rarest colors and the stone retains this hue for a period of time after UV exposure. Experts who have examined it so far consider it to be unique but the exact rarity of the stone will have to be established by a laboratory.

It is the property of mining companies Etruscan and Mountain Lake who plan to sell it by auction to a private collector. Les Meyer, a director of National Diamond Marketing, said, “I have had cause to view several million of stones but I have never come across a diamond of this nature, which leads me to believe that it is incredibly rare. It’s an exceptional piece due to the vibrant pink fluorescence and it has caused excitement amongst all who have examined it at National Diamond Marketing. Nobody can quite believe the color transition.”

Crystal-pulled Synthetic Chrysoberyl

(via Gemmology Queensland, Vol.1, No.2, February 2000)

According to Dr Hisashi Machida, of Japan’s Kyocera Corporation, Inamori currently produces twelve (12) synthetics for gem purposes. These man-made materials include flux-grown emerald, flocculated silica based plastic impregnated white and black opal, and synthetic alexandrite, cat’s eye alexandrite, blue sapphire, ruby, star ruby, pink sapphire, yellow sapphire, padparadscha sapphire, and green chrysoberyl which Machida claims are synthesized by a combination of a flux process and pulling.

Japan’s Kyocera Corporation has been producing gem quality Czochralski grown (crystal pulled) synthetic chrysoberyl for many years. While yellow (Fe³+ bearing), colorless, and Cr³+ containing alexandrite chrysoberyls have been available for some years, green and pink chrysoberyl have only recently been added to the product list.

The light green colored synthetic chrysoberyl is virtually inclusion-free, and is colored by V³+ of similar concentration to that found in Tunduru chrysoberyl of comparable color. Detectable quantities of Fe, Ga, and Sn were not found in the Inamori crystal-pulled synthetic chrysoberyl.
A bluish green synthetic chrysoberyl of possible Russian origin, was colored by five times the V³+ found in equivalently colored natural chrysoberyl, about 0.2 wt% Cr2O3. Like the Inamori synthetic, this green synthetic chrysoberyl had no detectable Fe, Ga, Sn.

An experimental pink synthetic chrysoberyl was colored by Ti³+ (the same chromophore that is found in hydrothermally grown pink synthetic beryl. This synthetic also was virtually inclusion free.

Identifying Synthetic Moissanite

(via Gems & Jewellery News, December 1998) Jamie Nelson writes:

If a large batch of unmounted diamonds of a range of sizes requires to be checked to determine if the batch has been salted with synthetic moissanites, then there is an easy alternative method to the methylene iodide sink or float separations.

Place the stones, table down, on the bottom of a shallow, flat bottomed, clear glass dish and cover all the stones completely with tap water. The much higher optical dispersion of moissanite (0.104 or almost x 2½ that of diamond) will reveal itself as bright spectral colored flashes, while diamonds (dispersion 0.044) will display less brightly colored sparkles. The method will still work with open-backed bracelets, necklaces and other items provided that all the stones lie table down (i.e. culet uppermost).

This being so, in the case of a finger ring mounted moissanite, the only piece of equipment needed to ensure a confident distinction is a battery-operated hand-held polariscope. The ring is placed between the polars so that the place of the stone’s table lies parallel to the optic axis of the polariscope, i.e. the long torch battery stem. The polariscope is then rotated in the axis of the torch barrel while keeping the ring stationary.

If the stone is moissanite, the usual winking of the stone’s image will be seen. If it is diamond, little or no change in the scattered light intensity will be observed. If the colorless stone happens to be another uniaxial or biaxial material, such as zircon, rutile, lithium niobate, corundum, scheelite, zincite, topaz or enstatite, then of course winking effects also will be seen. But all will be unable to pass a scratch-hardness test using the sharp edge of a carborundum (alpha silicon carbide) monocrystal applied cautiously to the girdle. However, our concern here is only to disclose the presence of moissanite and not to identify a nondiamond stone.

Synthetic Aquamarine

(via Gemmology Queensland, Vol.1, No.2, February 2000)

Tairus first produced light to dark greenish blue synthetic aquamarine in Russia in the mid-1990s. It is synthesized hydrothermally, and owes its greenish color to small amounts of Fe²+ and a Fe²+ - Fe³+ charge transfer mechanism. It is grown as flat tabular crystals on seed plates oriented at an angle to the c-axis.

Hyrothermally grown synthetic aquamarine has the following gemological properties:
Color: Light to dark greenish blue
Specific gravity: 2.65 – 2.70
Refractive index: 1.587/1.580 – 1.571/1.577
Birefringence: 0.004/0.008
Pleochroism: Weak to strong blue/colorless
Fluorescence (UV): Inert
VIS absorption spectrum: Bands at 800nm (Fe²+ ), 375nm ( Fe³+ ), shoulder at 650nm (Fe²+ - Fe³+ charge transfer, line at 400nm (Ni³+)

It can be discriminated from natural aquamarine by its:

- Chevron-like growth banding that parallels the seed plate. This growth banding which is made up of pyramidal sub-cellular growth subunits is typical of hydrothermal growth occurring of seed plates oriented at an angle to its c-axis.

- Occasional presence of flake-like aggregates of Ni-pyrrhotite and Ni-pyrite.

Chemical analysis will reveal Ni³+ as a contaminant from the walls of the autoclave in which the synthetic aquamarine was grown.

Deep Diffusion Treatment Of Corundum

(via ICA Early Warning Flash, No. 32, February 16, 1990) GIA writes:

General background
At one of the gem shows held in Tucson, Arizona, during February of 1990 one exhibitor was offering for sale blue sapphires which were reportedly enhanced with a ‘deep’ diffusion treatment. The authors of this report were shown two plastic bags of reportedly treated material, each containing an estimated several hundred carats of these treated stones. A number of these were purchased for investigation.

Gemological properties
Eleven treated stones were examined. Basic gemological properties—refractive index, birefringence, optic character, Chelsea filter reaction—were all consistent with those reported in the literature for natural blue sapphires.

The color of the stones was fairly uniform, being a medium dark slightly violetish blue. All were very transparent.

None of the stones exhibited any absorption features of the type association with iron-bearing blue sapphires. Three of the stones, however, exhibited a bright fluorescent line centered at 693nm. It is interesting in this regard that the vendor’s promotional flier states that ‘….all stones treated are genuine Ceylon sapphires…’

Key identifying features
Under longwave ultraviolet radiation all but two of the stones were inert; these same stones all fluoresced a weak to moderate, chalky yellowish green to short wave ultraviolet. The other two stones fluoresced a weak to moderate pinkish orange to longwave ultraviolet; the shortwave reaction was similar but weaker in intensity. None of the stones exhibited any phosphorescence.

Magnification and darkfield illumination revealed some features associated with corundum that has been subjected to high temperatures: diffused color banding, broken ‘dot-like’ acicular inclusions, melted included crystals resembling ‘snowballs’ with surrounding spatter halos, and superficial sintering in surface pits. It should be noted that these features were, in general, minor.

Examination using diffused transmitted light without immersion or magnification showed color concentrations along facet junctions and outlining of the girdle edge. Also noted was some variation in color from one facet to another.

Using immersion and diffused transmitted light without magnification the color concentrations along facet junctions and the girdle as well as the uneven facet-to-facet coloration were again noted. In many cases these features were significantly more obvious when immersion was now used.

Suggestion
Diffusion treated sapphires are now being made increasingly available in the market. It this becomes important to use diffused transmitted illumination and immersion in the routine examination of corundum.

The Shawshank Redemption

Memorable quote (s) from the movie:

Andy Dufresne (Tim Robbins): You know what the Mexicans say about the Pacific?

Red (Morgan Freeman): No.

Andy Dufresne (Tim Robbins): They say it has no memory. That's where I want to live the rest of my life. A warm place with no memory.

Hardness Testing Of Gemstones: A Re-evaluation Of The Values

(via Gemmology Queensland, Vol 3, No.1, Jan 2002/IGC Conference Madrid 2001) Michael Gray writes:

Hardness testing is one of the methods that a mineralogist uses to determine the identity of a mineral sample, but which has rarely been used by the gemologist. A mineralogist can usually find some inconspicuous face or broken area to conduct a scratch test, but the gemologist rarely has had a surface on a gemstone to do a comparable test without visible damage to the polish of the stone. However, the ability to choose a random surface may give a false value when a range of hardness exist, as in the case of kyanite, which has a documented variation from 4.5 to 5 on the Moh’s scale of hardness. While a species with such a diverse range can be easy to identify and test, there are many other species that have smaller variations that have not been measured. We are preparing a method of testing hardness during the faceting process. Our present system was developed by Friedrich Mohs in 1822, whereby he set relative values of hardness to ten easily obtainable species for comparison to each other, and measured by making scratches on surfaces of the unknown material with these ten species. This scale is still used as the standard, but variations in hardness has been known since at least 1844 using a device called sclerometer, and researchers were able to deduce objective values, although some variations in these scales are noted, depending upon the method and preparation used. In fact, some researchers determined that topaz is less hard than quartz when the sclerometer was used on powders of these two species.

Lapidaries have always noticed some of these variations in hardness in some species, especially noticeable in heat treated sapphires and rubies. A good example of this variation is the species fresnoite. In the references, the published hardness varies from “3 to 4” to a value of 4.7. A lapidary must rely upon these figures to determine which cutting and polishing laps and media to use in fashioning a gemstone. A great variation in hardness was noticed in the grinding and polishing of the stone, with only one direction being noticeably ‘soft’ as compared to the other facets. There is only one direction being in the range of 4 in hardness, with all other directions being noticeably harder.

These are hardly the only examples to cite; there are many materials, such as spodumene, sillimanite, elbaite, and many of the garnets that exhibit some noticeable variation in hardness during faceting. Diamond cutters know of the variations in their specialty, and use that knowledge in the fashioning of those gems.

The argument could be made that Moh’s scale has worked for almost two centuries, and that there is n need to change this system. That is not the purpose of this study. There are a number of purposes why this study has been initiated to determine the actual hardness of a species, such as fresnoite, where the original description may be inaccurate to document the variation of hardness, as well ad ‘normal’ hardness, within a species. To determine if a variation of hardness may be caused by a man-induced treatment, such as heat treatment of corundum, which then can be used as a way of detecting these treatments. This might also be taken further to determine origin, as well, depending upon impurities, coloring agents, and variations in chemical composition to help clear up conflicting values in different publications to relate these values to the existing Moh’s scale of hardness so that the numbers are understandable to academics and lay persons alike.

Equipment has been developed recently that makes it much easier to conduct hardness testing. The development of ultrasonic indenters that can be calibrated based on the Rockwell and Vickers scales, two of the glass and metal industry’s standards, should eliminate most of the danger of stone breakage during hardness testing. Our testing will be done during the cutting stages, so any noticeable marks made on the softer stones can be polished out.

The ten species used in the Moh’s scale will have been measured, resulting in a set of numbers that will set the parameters for the decimal places between species. Stones are being faceted of these materials to make note of any noticeable variations during cutting, and then measurements taken of these materials. After these values are established, checked, and documented, other species will be faceted, with noticeable hard and soft areas marked for testing. On stones with variable hardnesses, at least four hardness tests will be performed, one each on the ‘softest’ and ‘hardest’ directions, since these normally occur only in one direction, and several tests to establish the ‘normal’ hardness, the hardness over the rest of the material. Therefore, while a range may be established, a third number may represent the general hardness of the material.

The practicality of using gemstones for hardness testing is the general ‘purity’ of the sample being used. Many of the published hardness values were obtained using tiny pieces of the type specimens when they were first discovered and therefore were probably unable to get much accuracy, especially minerals described prior to the 1960s. Unfortunately, once a mineral is named and documented, the values may come up dependent upon the locality and/or if the material has been treated, and all of this information will be documented, as well, whenever possible. Ultimately, we should be able to document the crystal orientation that these variable hardnesses will occur.

There is also an important side benefit to this testing. While hardness testing is only used in a miniscule number of gem identifications, we hope to show that this test can be used in gem labs, using the modern equipment available today. The marks made by a skilled and knowledgeable worker using this modern equipment can be so tiny as to be undetectable by the naked eye, and can be placed on an inconspicuous spot on the girdle or pavilion of the stone. With the values obtained through this research, there will be one more test available for questionable gems. It should also be possible to test mounted stones as well, where refractive indices and specific gravities may not be able to be obtained without removal of the stone from the mounting.