Winning Submission of the 2009 Gemology Project Challenge
- 1 Introduction
- 2 Father of Origin Determination: Dr. Eduard (Edward) J. Gübelin
- 3 Mine Production
- 4 Origin Determination
- 5 Corundum
- 6 Gemstone Formation
- 7 Characterization of Gemstone Properties
- 8 Techniques Used for Origin Determination
- 9 Challenges for Origin Determination
- 10 Benefits of Origin Determination
- 11 Intellectual Requirements
- 12 Sources Consulted
- 13 External link of interest
- 14 Acknowledgements
- 15 Special permission required
Collectors of gemstones and minerals often attach great importance to a gemstone’s provenance or country of origin. In "A Question of Origin," according to Mr. Richard W. Hughes, (1990, , n.p.), formerly, there was no method of geographical origin determination for colored gemstones or diamonds; a gemstone or diamond’s “mine-type” was strictly based on overall quality and appearance or color. For example, a ruby of an “intense, highly fluorescent red” was sometimes called “Burma-type,” or “Burma-like,” even when the ruby was not mined in Burma. In the 1940’s and 1950,’s the GIA, along with others in the gemology field, developed the system of quality analysis for diamonds; and mine-types were no longer used in describing diamonds. Some examples of the mine-types used to describe diamonds are “Golcondas” or “Premiers,” and several others. Also, during the ‘40’s and ‘50’s, studies initiated by Dr. Eduard J. Gübelin, proved that it was possible to identity a gemstone’s geographical origin and sometimes even the exact mine it came from based on the gemstone’s inclusions rather than using its overall appearance (Hughes, 1990, A Question of Origin, , n.p.).
Father of Origin Determination: Dr. Eduard (Edward) J. Gübelin
The late Dr. Eduard J. Gübelin of Lucerne, Switzerland “devoted his life and career to unveiling the mystique of gemstones and was recognized as the authority on inclusions in gemstones. His great knowledge of mineralogy and the jewelry business combined with his passion and admiration for gemstones made him one of the founders of modern gemology and the father of gemstone origin determination (Gübelin Gem Lab, Ltd., n.d., “Legacy of Dr. Eduard J. Gübelin,” , n.p.).” During his 70-year career, Dr. Gübelin collected over 5,000 rare and commercial gem specimens, which included organic gemstones, from different localities. He began to determine the origin of gemstones by systematically documenting, classifying, and categorizing gemstone specimens he collected from the mines and locations he toured. Based on the microscopic features or inclusions in the gemstones he established a “strict characterization” of gem deposits. “His concept is based on the comparison of a gemstone of unknown origin with gemstones of known origin; by determining their similarity, and the degree of resemblance of gemstones from different mining sources (Gübelin Gem Lab, Ltd., September 2006, A Holistic Method to Determining Gem Origin, , p. 122).” In the early 1950’s, Dr. Gübelin’s gemological studies led to an increase in the interest of different mining sources, the science of gemstone geographical origin determination, and gemological laboratory country-of-origin reports which are used by every auction house today.
Mines produce a wide variety of gemstones, usually of low to medium quality, with the finer gemstones forming only a “tiny fraction of the whole production,” including those which are found at the most prestigious sources. The precious gemstones, ruby, sapphire, and emerald, may show price variations and some command premium prices based on their provenance since part of the colored gemstone marketing and branding concept includes origin, even though these stones may not always be of high quality. “Origin” should not be used to reflect a certain quality of colored gemstones, nor should it be used as a description of a color type (Hughes, 1990, A Question of Origin, , n.p.). Today, some top-quality gemstones from recently discovered deposits, such as the sapphires found in Madagascar, with similar geology as their highly-valued gemstone counterparts, are not only impressive, but are also found in remarkable sizes; yet, since they are not from a well-known or prestigious source, they are accepted as nothing more than beautiful stones by most in the trade (Gübelin Gem Lab, Ltd., July 2006, The Roots of Origin Determination, , p. 66). With the exception of spinel, tourmaline, pink topaz, and alexandrite, geographic origin determination is not yet available for other gemstones.
Recognized for being largely responsible for the development of the science of origin determination pioneered by Dr. Eduard J. Gübelin, Gübelin Gem Lab, Ltd., determined that it is a “key requirement” for gemological laboratories to have access to an authentic and complete collection of reference stones, which have had their gemological properties properly analyzed and fully documented, and their geologic-genetic environment is known (Gübelin Gem Lab, Ltd., July 2006, The Roots of Origin Determination, , p. 69). The reference stone collection must contain a sufficiently high number of samples from commercially relevant mining areas and deposits worldwide which include reference stones from exhausted mines or deposits where production has ceased. It is usually very rare to be able to collect samples directly from the host rock in the mine. The research field gemologist collects sample stones from mining areas and deposits worldwide by adhering to strict criteria and guidelines for collection. Extreme care and caution are recommended before samples can be incorporated into a reference collection because receiving stones from a source other than one claimed can have disastrous results. The process and method which the sample stones are collected is fully and properly documented; and then, are compared with the analytical data from the reference collection, or gemstones from a known source, such as the mining area, geographic location, or country, to determine and confirm the origin of the collected samples. One problem research field gemologists face is that of maintaining a current and reliable population of sample stones. Since new material is being found almost daily, tracking changes of the properties and chemistry of new and old deposit production can be a daunting task (Gübelin Gem Lab, Ltd., September 2006, A Holistic Method to Determining Gem Origin, , p. 126). For example, the best reference stone population of Ceylon sapphires collected 20 years ago may not be as valid for comparison as recently collected samples might be (Hughes, 1990, A Question of Origin, , n.p.). Therefore, gemological laboratories must continuously acquire new information through research that must be repeatedly updated. Samples must be collected and updated from mines that are open or reopen every year worldwide. Some colored gemstone mines or deposits may become depleted or inaccessible due to socio-political complications which can make it quite difficult for the research field gemologist to collect specimens. Providing information on the geographic provenance of a stone is the goal of the origin determination process.
Therefore, “the goal of origin determination is to provide the geographic provenance of a gemstone and can be defined as:
- the attribution of a stone to a specific geological-genetic environment (or a specific type of deposit) and
- the attribution of a stone to a mining area, a geographic locality, or country (Gübelin Gem Lab, Ltd., July 2006, The Roots of Origin Determination, ,p. 69)
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.).”
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, , 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, , 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, , 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:
- 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:
- High-temperature enhancements will provoke the thermal alteration of most mineral inclusions and may complicate the origin determination process.
- 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, , n.p.).”
- Chemical “fingerprinting” such as minor, major, and trace elements:
- 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.
- The incorporated minor elements depend on local geological conditions, such as temperature, reduction-oxidation reaction, and chemistry.
- Optical properties including birefringence and refractive indices
- Infrared characteristics
- Luminescence behavior (Gübelin Gem Lab, Ltd., July 2006, The Roots of Origin Determination,  p. 68).”
- Spectral fingerprinting:
- UV-ViS-NIR-range: Approximate spectral ranges used in gemology:
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:
- Optical analysis by microscope (Figure 1)
- Spectroscopic analysis in Ultra violet-Visible-Near Infrared (UV-ViS-NIR) (Figure 2)
- Raman spectroscopic analysis using a Raman spectroscope (Figure 3)
- Spectroscopic analysis by Fourier Transform Infrared Spectrometry (FT-IR) (Figure 4)
- Chemical analysis by Energy-dispersive X-ray Fluorescence (ED-XRF) (Figure 5)
- Chemical analysis by Laser-induced Breakdown Spectroscopy (LIBS) (Figure 6)
- Chemical analysis by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) (Figure 7)
- Surface analysis by SEM (Scanning Electron Microscope) (Figure 8)
- 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.
Challenges for Origin Determination
How do laboratories determine the country of origin if gemstones are formed in similar genetic environments or geological and mineralogical conditions, yet, their geographic regions are located great distances apart? For example, sapphires originating from the Sri Lankan and the Kashmir region have similar or overlapping gemological properties, which make determining a separation between the sources almost impossible. With the scenario of gemstones having very similar properties which are from different locations, instead of searching for one diagnostic feature to separate the sources, a comprehensive view of the gemstones is considered, such as the identification and description of inclusions, analysis of chemical elements, and spectral properties. “Evaluation and interpretation of the observed features, combined with additional advanced analysis,” may allow a laboratory to reach a conclusion on the geographic origin of the gemstones (Gübelin Gem Lab, Ltd, August 2006, The Limitations of Origin Determination, , p. 62).
There are also various mines and deposits, which are scattered over a geographical location and categorized as a single entity, such as the Montana sapphires found in the United States, which produce stones which differ not only in color, but also inclusions. Sapphires from the Missouri River mines differ from those found at Yogo Gulch as well as the sapphires found at Rock Creek. Unfortunately, in this case, there is no distinction between the localities of the deposits, even though each of the deposits produces sapphires with differing and distinct characteristics (Hughes, 1990, A Question of Origin, , n.p.)..
Laboratories that provide origin reports are vulnerable when new gemstone treatments, synthetics, or newly discovered material enter the market. It is necessary that the laboratories are able to research new finds by visiting the new deposits or mines, and research new treatments and synthetics possibly before they enter the market. One scenario laboratories may face is when a consumer’s colored gemstone is sent to 2 different laboratories for origin determination with differing results of the stone’s provenance from each of the labs. The consequences may be dire for the consumer. For example, at the May 2009 ICA Congress Speech of Dr. Adolph Peretti, Dr. Peretti shed light that the “misinterpretation of a gemstone’s origin may possibly provide a gem dealer with a huge premium. If a consumer sends the gemstone, for example, a ruby, to one laboratory for origin determination, which declares the ruby of Burmese origin, and then the consumer sends the ruby to a different laboratory, which concludes that the ruby is of Vietnamese origin, the consumer may lose the amount of money the dealer made with his initial premium. The ruby mentioned in the hypothetical scenario was from a new deposit and had not been examined by laboratories for origin testing before it entered the market and was sold to a consumer (ICA Congress Speech of Dr. Adolph Peretti, May 2009, "Research report summaries on the origin and treatments of valuable rubies from Tanzania and tourmalines from Brazil and Mozambique," , n.p).” However, the percentage of these conflicting origin reports is relatively small. Misidentifying the origin a gemstone is usually an unfortunate consequence of the lack of funding and research needed to provide accurate origin determination, but, it is a necessity that labs are able to ensure the integrity of their gemstone country-of-origin reports. If the origin for a gemstone cannot be determined, laboratories will state that “no origin” could be determined for the gem in question. For example, when a laboratory tests a stone for its geographical location, but findings of the gemological test results and observations are insufficient, or uncertain, the opinion of the gemstone’s origin should not be given.
Dr. Peretti discussed another challenge for laboratories which provide origin reports are the problem encountered in the gemstone market which involves the provenance of Paraiba Tourmaline. Paraiba Tourmaline, originally discovered in the state of Brazil in 1989, is a copper-bearing tourmaline of greenish-blue color and the most valuable tourmaline in the world. The recently discovered copper-bearing tourmalines from Mozambique, as well as those from Nigeria, are being called “Paraiba Tourmaline,” by some laboratories and gemstone dealers, regardless of their origin. “Comparison of statistics of copper-bearing tourmaline from Mozambique and Brazil show that different colors and sizes are found from both origins. In general, copper-bearing tourmalines from Mozambique have more color varieties, while tourmalines from the state of Brazil are more color intense at equal sizes.” A “non-educated” consumer may believe he or she is purchasing a Paraiba Tourmaline from Brazil, when actually in reality, the tourmaline is from Africa. Since a huge price difference exists between the origins of copper-bearing tourmalines, with the Brazilian Paraiba Tourmalines commanding much higher prices, this dilemma “may lead into legally critical situations (ICA Congress Speech of Dr. Adolph Peretti, May 2009, "Research report summaries on the origin and treatments of valuable rubies from Tanzania and tourmalines from Brazil and Mozambique," , n.p).”
Benefits of Origin Determination
At the 2007 ICA Congress Lab Session, Mr. Christopher P. Smith discussed with attendees that gemstone geographic origin determination is not “an exact science” and is still in its infancy. Also attending the session, Mr. Vincent Pardieu stressed the necessity and importance gem laboratories must not only strive to keep up with technology related to treatments and synthetics; but also research new gem deposits to keep up with the growing demand for origin determination reports. (ICA Congress Lab Session, May 2007, "Labs Tackle Question of How to Help Industry, Build Consumer Confidence at ICA Congress," , n.p.). With the 2008 United States of America government ban on the importation of rubies from Burma into the US still in effect, county-of-origin determination, particularly for corundum, has additional importance to the trade as well as consumers. Origin reports may have a serious political purpose when they are used to prevent the unregulated sale (smuggle or launder) of “conflict gemstones” (Lesney, 2001, Precious Provenance, , n.p.). Thus far, the attempt to implement a system, similar to the Kimberely Process for diamonds, to ensure that a ruby is not from Burma, has been unsuccessful since the “majority of ruby-producing areas are highly decentralized. Other ruby deposits discovered in Africa, such as the beautiful and usually unenhanced Winza ruby, recently discovered in Tanzania Country, show promising alternatives for sources which may produce gem-quality stones. In 2002, Columbia Gem House of Vancouver, Washington, in the United States, implemented a mine-to-market promotion to bring rubies into the U.S. from Malawi by developing a local mining industry and partnering in community and social developments (Smith, et al., 2008, Inside Rubies, p. 141).”
Understanding the genesis of gemstones helps in the determination of their geographical origin, thus improving prospecting strategies for mining gemstones, such as corundum, which could also be used as a method for controlling the trading circuits. The need for 3rd party certification for gemstones from gemological laboratories, including country-of-origin reports, can also help support and grow the industry. Consumers of gemstones not only want to know the gemstones they purchase are being identified properly and that they are reasonably priced, but, also, they also want to be reassured that the gemstones are from conflict-free sources. Laboratories hope to build and sustain consumer confidence through the issuance of colored gemstone country-of-origin reports. Today, consumers purchase over 50% of gemstones via television shopping networks and the internet which has forced traditional jewelers to reexamine how they sold gemstones. Jewelers are now more likely to provide gemstone provenance with gemstone identification reports for their high-end gemstones. Laboratories also work closely with those in the trade to be able to provide origin reports and certificates for gemstones at a reasonable price, as well as educating people in retail to speak confidently about the gemstones they sell (ICA Congress Speech of Dr. Adolph Peretti, May 2009, "Research report summaries on the origin and treatments of valuable rubies from Tanzania and tourmalines from Brazil and Mozambique," , n.p).
Most gemological laboratories invest a certain amount of their resources in scientific research activities, which is usually used “in-house,” but, is also shared with the gemological and geological communities through research publications. An effective way of obtaining first-hand access to scientific results is through the cooperation of researchers and research organizations (Gübelin Gem Lab, Ltd., September 2006, A Holistic Method to Determining Gem Origin, , p.126). .
Origin determination requires a thorough understanding of the geological processes. The “interpretation of small-scale gemological observations requires constant verification with the scientific models of large-scale geological environments (Gübelin Gem Lab, Ltd., September 2006, A Holistic Method to Determining Gem Origin, , p.126).” It is recommended that most gemologists at a gemological laboratory, who are involved in origin determination, hold a degree in the earth sciences, such as mineralogy, petrology, crystallography, geology, or a related field. To be able to successfully tackle the challenges of origin determination, this academic foundation should be complemented with “solid” gemological training and several years of experience in a gem lab. The analysis of gemological properties and interpretation of the resulting data and observations alone exceed the level of knowledge taught in standard gemological training (Gübelin Gem Lab, Ltd., September 2006, A Holistic Method to Determining Gem Origin, , p.126).
- Gemstone Buzz. Retrieved October 2009, from http://www.gemstonebuzz.com
- GIA Research (Thailand). Retrieved October 2009, from: http://www.giathai.net/lab.php
- Hughes, Richard W. (1990). A Question of Origin. Gemological Digest, Vol. 3, No. 1. Retrieved October 2009, from: 
- ICA Congress Lab Speech. (2007, May). "Gem Labs Tackle Question of How to Help Industry, Build Consumer Confidence at ICA Congress." Retrieved October 2009, from: http://www.gemstone.org
- ICA Congress Speech of Dr. Adolph Peretti. [unpublished speech.] (2009, May). "Research report summaries on the origin and treatments of valuable rubies from Tanzania and tourmalines from Brazil and Mozambique." Source: http://www.gemresearch.ch
Retrieved October 2009, from http://www.gemstone.org/congress/panyu2009/speakers-presentations/Adolf_Peretti/Talk-DrPeretti-translation1-EBsuggestions.doc
- Kane, Robert E., Boehm, Edward W., Overlin, Stuart D., Dirlam, Dona M., Koivula, John I., and Smith, Christopher P. (Winter 2006). A Gemological Pioneer: Dr. Eduard J. Gübelin. Gems & Gemology, Vol. 41, No. 4, pp. 298–327. © 2005 Gemological Institute of America.
- Legacy of Dr. Eduard J. Gübelin. (n.d.). Retrieved October 2009, from: http://www.gubelinlab.com (n.p.).
- Lesney, Mark S. (2001, March). Precious Provenance. (n.p.). Today's Chemist at Work. Retrieved October 2009, from: 
- Pardieu, Vincent. (2008, December-2009, February). Concise Field Report, Vol. 1, Palin, Cambodia. Gemological Institute of America Laboratory, Bangkok. Retrieved October 2009, from: 
- Rossman, George R. (2009, June). The Geochemistry of Gems and Its Relevance to Gemology: Different Traces, Different Prices. Elements, Vol. 5, pp. 159-162. Retrieved October 2009, from: http://www.elementsmagazine.org/
- SSEF, Swiss Gemmological Institute. Retrieved October 2009, from: http://www.ssef.ch/index.html
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- The Gübelin Gemmological Laboratory, Ltd. (2006, July). The Roots of Origin Determination. Jewellery News Asia, pp. 66-71. Retrieved October 2009, from: 
- The Gübelin Gemmological Laboratory, Ltd. (2006, August). The Limitations of Origin Determination. Jewellery News Asia, pp. 52-62. Retrieved October 2009, from: 
- The Gübelin Gemmological Laboratory, Ltd. (2006, September). A Holistic Method to Determining Gem Origin. Jewellery News Asia, pp. 118-126. Retrieved October 2009, from: 
External link of interest
AN EXCELLENT RESOURCE AND HIGHLY RECOMMENDED WEBSITE ON FIELD GEMOLOGY AND ORIGIN DETERMINATION: “A travel blog to the mysterious origins of gemstones! Where passion for gemology (gemmology) and travel meets!” Vincent Pardieu’s Field Gemology, http://www.fieldgemology.org
Special thanks to Mr. Edward Boehm, grandson of the late Dr. Eduard (Edward) J. Gübelin, of JOEB Enterprise for providing corrections, contacts, and excellent suggestions, and to Dr. Eduard J. Gübelin’s family for permitting use of the family’s special photograph of Dr. Gübelin, and to Gübelin Gem Lab and staff of Lucerne for permitting use of many of the photographs and resources.
Further thanks go to owner and President of AGL, Mr. Christopher P. Smith, and American Gemological Laboratories staff for the resources on source-type classification, providing reprints of the AGL reports, answering questions, critiquing the essay, and providing photographs and to Mr. Vincent Pardieu, Supervisor for Field Gemology at GIA Laboratory of Bangkok, for answering inquiries and the use of many of his photographs. Thanks to Dr. Michael S. Krzemnicki, Director of SSEF, Michael Stubelt of New Wave Research Company , and WikiMedia Commons for permitting use of photographs.
Special permission required
The photographs used with the essay are protected by copyright laws. All of the photographs used with the essay require special permission for their use, with the exception of photographs used from WikiMedia Commons. These terms also apply to the resource material used in the essay.
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