AZGem Gems

June 2016

 

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The World's Most Useful
Gem & Jewelry Monthly Newsletter

Written by Carolyn Doyle for customers of
The Dorado Company

and other visitors to the azgem.com website who subscribe.

 

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Usable Gems... and a little opinion.

  

Colored Gemstone Country of Origin 

 

colored gemstone country of origin

Image credit: Sotheby's

 

This Colored Gemstone Country of Origin article continues our discussion from last month. Thanks to The Gemology Project in-depth articles on this and many other gemology-related subjects are available on the internet.

The ability of commercial gem testing and grading laboratories to scientifically determine the origin of commercially important gemstones can be very important to a gemstone and jewelry devotee. As we discussed last month, a quality blue sapphire known to be from Kashmir is more valuable than a similar appearing gem of other origin.

Gem dealers and auction houses rely on the commercial gem testing labs for origin testing.

Buyers of high-end gems… and jewelry featuring high-end gems are often knowledgeable and discriminating in their choices. They may prefer gems with certain origins for a variety of reasons, including rarity, enhanced value, and bragging rights.

 

 

colored gemstone country of origin

Image credit: Sotheby's

 

Colored gemstone country of origin is often an important consideration for museums and private gem collectors in their acquisition of a gemstone or gem specimen. Most museums also rely on these same commercial gem labs. Few expend the resources necessary to run their own labs.

Colored gemstone country of origin determination was pioneered by a few gem institutions with a scientific and academic mission, primarily the Gübelin Gem Lab, the American Gemological Lab, and the Gemological Institute of America. Fortunately, both institutions offer their services to the gem industry on a fee basis.

These labs continue to lead the way, employing the best equipment, practices, experience, and most complete collection of mine-documented comparison stones.

 

 

 

colored gemstone country of origin kagem open pit emerald mine, zambia

Image credit: Gemfields

 

colored gemstone country of origin sri lanka gem mine

Image credit: GIA

 

Comparison stones are usually collected by representatives of the institutions themselves. They go into the field to visit important gem mines and mining districts all over the world. They study the geology and collect sample gemstones. Most mines and mining companies support the advancement of scientific knowledge by welcoming the representatives and donating the samples. The mines may be industrial scale operations or simply artisan mining by locals. Almost everyone cooperates.

The gemstone samples are documented as to origin, and rigorous procedures are followed to assure no mix-ups occur in the field, or later in the lab.

 

 

 

colored gemstone country of origin burma ruby

Image credit: Sotheby's

 

Colored gemstone country of origin determination services by commercial labs is often limited to ruby, sapphire, and emerald gems, but this is a result of economics, not science. There is no commercial demand for a service to determine the origin of a one hundred dollar per carat spessartite, or many other gems. The labs still collect samples and study these gems pursuing scientific knowledge.

 

colored gemstone country of origin spessartite garnet

Image Credit: Omi Prive

 

The Colored gemstone country of origin determination report from the Gemology Project - Part One, was reprinted in the space below in the May, 2016 (last month's) edition of this newsletter. This month, more of the report is published,

This report is written for gemologists, academics, and research scientists. It can be complicated. Don't worry about the detail, a casual reading will give you a general idea of gemstone origin determination.

 

Origin Determination – Continued from last month

This information is courtesy of The Gemology Project

Corundum

Rubies and sapphires belong to the corundum mineralogical family. At one time, corundum was regarded as a rare mineral, until it was realized that it was of more frequent occurrence than once supposed. For example, today, in approximately 20 countries around the world, gem-quality ruby can be found. Corundum is formed in several distinct ways and under various conditions; and the geological environments from which they are formed have a direct impact on the properties and characteristics of corundum (Smith, et al., 2008, Inside Rubies, p. 147).

Source-Type Classification of Corundum

Gemological laboratories are now able to determine the geological localities of corundum by their properties, characteristics, and understanding the genetic environment from which they were formed. “Through years of experience, Mr. Christopher P. Smith, with the American Gemological Laboratories, have proposed a new “source-type” classification for gem corundum that is based on the precept that the geologic environments of their formation give rise to certain distinctive characteristics in which they occurred, as well as an indication of the particular geographic localities from which they may have been found. This system of classification has been given the name, “source-type,” as a reference to the broad application of the word, “source.” Source-type may not only refer to a geologic source, but may also be indicative of a geographic source as well (Smith, et al., 2009, Corundum – Source Type Classification and Geographic Origin Declarations: Part I, n.p.).”

According to Mr. Christopher P. Smith and American Gemological Laboratories (2008), “this classification has two tiers; the first tier separates corundum into three groups based on broad geologic formation features. Two of these groups possess what are considered to be “classical” combinations of specific gemological features, which occur in metamorphic and magmatic-related environments. The third group incorporates corundum that possesses combinations of features, properties, and characteristics outside of the two “classical” groups, and may have derived from either a metamorphic or magmatic-related deposit (Inside Rubies, p.147).” “The second tier of the classification system subdivides each of these three groups into four categories or “types,” Types I-IV, based on their dominant inclusion features and supported by various other analytical techniques and data from advanced analytical techniques. Combinations of these types may also occur when multiple features are encountered in a stone (Smith, et al., 2008, Inside Rubies, p. 148).”

“The source-type classification of corundum is also comparable with certain quality categories of rubies and sapphires already recognized by gemologists and the colored stone trade. It provides a practical parallel for such groupings, thereby permitting it to be used by gemologists, wholesale and retail trade, and even consumers. It may also be used to provide better clarity for the trade and consumers when used to compliment traditional geographic origin reports or declarations (Smith, et al., 2009, Corundum – Source Type Classification and Geographic Origin Declarations: Part I, n.p.).”

Gemstone Formation

The knowledge of a gemstone’s origin provides vital information on the geophysical processes under which it formed below the Earth’s surface. Traces of other minerals, or inclusions, found in a gemstone, provide information about whether it is natural or synthetic and may provide possible clues of its geographical or geological origin. In the gemstones of the same species which are found in different localities, such as the garnet species, the minor and trace elements are different, or incorporated differently, and may also be used as a tool for determining geographical or geological provenance. A gemstone’s gemological and mineralogical properties are controlled directly or indirectly by the environment in which it is formed. “The most relevant factors during natural gemstone formation are: 1) the nature of the host rock, 2) the nature of the host rock and the “interactive events” between the host rock and nearby rock units, such as exchange reactions involving the migration of fluids, thus introducing or taking away chemical components necessary or unwanted for the growth of a gemstone, 3) temperature and pressure conditions, and 4) composition and nature of solutions/liquids responsible for the dissolution, transport, and precipitation of the chemical components involved in crystal growth (Gübelin Gem Lab, Ltd., July 2006, The Roots of Origin Determination, [12], p. 66).”

Characterization of Gemstone Properties

The provenance of some colored gemstones is possible “because the full range of properties of a gemstone measured and observed in the gemological laboratory reflect the specific conditions of its genetic background during the natural crystallization process and are a direct consequence of the geological-mineralogical conditions of the surrounding host rock before, during, and after the growth of a crystal (Gübelin Gem Lab, Ltd., July 2006, The Roots of Origin Determination, [13], p. 69).” Origin determination is more reliable when a gemstone has a great number of individual and characteristic properties, such as its inclusions, growth structure, and physical and chemical properties that are clearly distinguishable from gemstones of the same locality or all other localities. These characteristics should not only positively identify a gem’s origin, but, should also eliminate other possibilities of origin. Gemological research laboratories use similar methods and processes for gemstone country-of-origin determination, such as using customized software, which allow for the processing and evaluation of observations, as well as updating current reference source information. Gemological analysis by a gemological laboratory may result in 10 to 50 observations of a single gemstone, although, some gemological laboratories use simpler methods of observation for origin determination. Some labs or gemological institutions have implemented a “phenomenological classification of gemstones in order to describe certain types of appearances of gemstones (Gübelin Gem Lab, Ltd., September 2006, A Holistic Method to Determining Gem Origin, [14], p. 126).” The origin determination process provides information on the geographic or geological provenance of colored gemstones based on data compiled during extensive gemological testing methods which should be non-destructive or at least “quasi non-destructive.” For example, LA-ICP-MS, which employs a laser ablation method, leaves a small crater of up to 200 microns on the surface of a gemstone. “The most important gemological-mineralogical criteria used for the characterization of gemstones are:

  1. Inclusion features such as growth features, natural cavity fillings such as fluid inclusions (must not be confused with fillings of fissures and open cavities due to man-made treatments), and solid inclusions:
  2. High-temperature enhancements will provoke the thermal alteration of most mineral inclusions and may complicate the origin determination process.
    1. It should be noted that the “study of inclusions is also a relatively new science; there are many gemstone inclusions that have yet to be identified and catalogued; and much to be learned about inclusions (Hughes, 1990, A Question of Origin, [15], n.p.).”
  3. Chemical “fingerprinting” such as minor, major, and trace elements:
    1. Minor and trace elements often determine the difference between a common mineral specimen and a gemstone; these trace elements are also often responsible for the color of gemstones.
    2. The incorporated minor elements depend on local geological conditions, such as temperature, reduction-oxidation reaction, and chemistry.
  4. Optical properties including birefringence and refractive indices
  5. Infrared characteristics
  6. Luminescence behavior (Gübelin Gem Lab, Ltd., July 2006, The Roots of Origin Determination, [16] p. 68).”
  7. Spectral fingerprinting:
    1. UV-ViS-NIR-range: Approximate spectral ranges used in gemology:
Ultra-violet: 280-390 nm
Visible range: 390-780 nm
Near Infrared: 780-1400 nm

Techniques Used for Origin Determination

Origin determination research with modern gemological tools may provide even further information to distinguish gemstones from different localities. Some of the laboratory tests and equipment used for origin determination by some laboratories are:

  1. Optical analysis by microscope
  2. Spectroscopic analysis in Ultra violet-Visible-Near Infrared (UV-ViS-NIR)
  3. Raman spectroscopic analysis using a Raman spectroscope
  4. Spectroscopic analysis by Fourier Transform Infrared Spectrometry (FT-IR)
  5. Chemical analysis by Energy-dispersive X-ray Fluorescence (ED-XRF)
  6. Chemical analysis by Laser-induced Breakdown Spectroscopy (LIBS)
  7. Chemical analysis by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS)
  8. Surface analysis by SEM (Scanning Electron Microscope)
  9. Isotope analysis (destructive) of corundum by using a databank for compiling the oxygen isotope concentration ratios for corundum of alsi basaltic-type places which requires access to the primary deposit to confirm the origin. Important and necessary tools to identify provenance of gemstones are ED-XRF, Raman spectroscopy, and ICP-MS.

 

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To be completed next month

 

 

Colored gemstone country of origin determination is a challenging field for gemologists. Chemical composition, trace minerals, typical microscopic inclusions, and other characteristics can identify where a gem was born, thanks to early gem industry professionals.

 

gem news

 

Photo Information

 

Top - Sri Lanka Sapphire

Next - Zambia Emerald

Next - Kagem Open Pit Emerald Mine, Zambia

Next - Sri Lanka Gem Mine

Next - Burma (Mogok) Ruby

Next - Spessartite Garnet

Next: - Gem special offer - Pearl Earrings 

Next - Industry News - Spinel added as August birthstone

Next - Dealer Product Image - Amethyst Ring in Sterling Silver

Last - Dealer Program Image - Pink Spinel and Sterling Silver Earrings

 

 

A Google search for links or images using keywords such as gems of sri lanka or spinel gem colors can return some very interesting information and websites.

 

Google

 

Gem Offer

 

gem special offer pearl studs

 

Here is this month's special gem deal. 

 

Gem:     Pearl Studs

Color:     White, pink blush

Quality:     Gem quality pearls, 14 karat yellow gold cups, posts, nuts.

Shape:     Round 

Dimensions:     6 mm

Approximate Weight:     .N/A

Price:     $33, plus shipping ($5)

Send me an email (with anti-spam) (carolynatazgemdotcom) and tell me that you want this fine gem.

We have other  shapes, sizes, and shades of gems available.

We keep gem prices low by buying quality gemstone rough worldwide, and having the rough material cut by our gem cutters in Asia.

 

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Gem Industry News

 

AGTA & JA to Add Spinel as an Official Birthstone for August

The revised birthstone list will launch to consumers later this summer

 

spinel is now a birthstone for august

 

Adding spinel as an August birthstone gives a complete range of color choices to those born in August.

Spinel, first cousin to sapphire and ruby, comes in just about every color imaginable. The most popular colors are reds, pinks, and blues.

Here is the News Release announcement from AGTA and JA...

New York, NY – The American Gem Trade Association (AGTA), the authoritative source on natural colored gemstones, and Jewelers of America (JA), the national trade association for businesses serving the fine jewelry marketplace, have announced that spinel will join the official list of birthstones as an additional gemstone for the month of August. The new birthstone will launch to consumers in July, through a public relations and marketing campaign led by JA, which established the modern birthstone list in 1912. 
“At certain moments in history, when there is a strong call from gem enthusiasts to expand the list of official birthstones, Jewelers of America believes in recognizing the importance of historically significant gemstones and giving gemstone lovers a choice that suites their preferences,” says JA President & CEO David J. Bonaparte. “Spinel is a welcome addition to August’s peridot birthstone, sure to be embraced by both jewelers and the jewelry consuming public.” “Ancient gemstone merchants revered spinel, and it was widely sought after by royalty. It was then known as ‘Balas Ruby’,” says AGTA CEO Douglas Hucker. “It wasn’t until the late 18th century that we developed the technology acumen necessary to distinguish spinel as a separate mineral from ruby. We are very excited to announce it as the newest member of the official birthstone list.” Two notable examples of spinel’s historical significance include a 170-carat red spinel, known as the famed “Black Prince Ruby,” that graces the Imperial State Crown in the British Crown Jewels; and a 398-carat red spinel – considered the largest ever found –atop the Imperial Crown of Russia, commissioned by Catherine the Great in 1763. “Spinel is an incredible gemstone that has garnered respect for centuries, and it is enjoying surging popularity because of its stunning range of colors,” remarks AGTA President Jeffrey Bilgore. 

“Birthstones have their roots far back in recorded history, strongly influenced by biblical teaching and related to the 12 stones in the breast plate of Aaron as well as the lunar calendar,” explains Hucker. 
This is the third update to modern birthstone list since it was officially created in 1912 by the American National Retail Jewelers Association, now known as Jewelers of America. It was updated in 1952, adding alexandrite, citrine, tourmaline and zircon as birthstones, and again in 2002, when Tanzanite was made an additional December birthstone. 
For more information on the promotional opportunities related to spinel’s public launch as a new August birthstone, check Jewelers of America’s website at www.jewelers.org/ja in the coming months. 
For more information, contact AGTA at 800-972-1162 and info@agta.org, or contact Jewelers of America at 800-223-0673 and members@jewelers.org. Additional information on spinel can be obtained at http://agta.org/gemstones/variation-spinel.html. For the official list of birthstones, visit http://www.jewelers.org/gift-guides/birthstone-jewelry-guide

 

 

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Jewelry Dealers

 

jewelry dealers wholesale

 

If you attended any of the Las Vegas Jewelry Week shows you are busy deciding how the loose gems you purchased should be turned into finished jewelry. If you bought loose gems from us instead of going to Las Vegas, you're probably doing the same.

Sales opportunities slow down this time of year... but they still exist. Mine your customer list for gift occasions... anniversaries, birthdays, and more.

Be The quality jewelry dealer at a lower price.

 

 

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Jewelry Dealers Program

 

jewelry dealers program

 

Do you enjoy jewelry and gems?

Do you enjoy talking with friends and friends of friends?

Could you use an extra income source?

Take a look at our great Jewelry Dealers Program.

 

 

Carolyn Doyle

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