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It is often difficult to obtain an expert judgement from a neutral laboratory. Analysis and estimation in the gemstone trade usually have to take place on site. Professional gemologists and gemstone buyers use mobile laboratories, which pool all necessary instruments in a travel case. Such so-called
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Rudimentary education in gemology for jewellers and gemologists began in the nineteenth century, but the first qualifications were instigated after the
National Association of Goldsmiths of Great Britain (NAG) set up a Gemmological Committee for this purpose in 1908. This committee matured into the
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minerals, show small flaws – short planar cracks where the direction of the crystalline orientation in the gem abruptly changes. The natural formation of gemstones tends to layer the minerals in regular crystalline sheets, whereas many synthetically produced gems have an amorphous structure, like
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The first gemological laboratory serving the jewelry trade was established in London in 1925, prompted by the influx of the newly developed "cultured pearl" and advances in the synthesis of rubies and sapphires. There are now numerous gem laboratories around the world requiring ever more advanced
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As with all naturally occurring materials, no two gems are identical. The geological environment they are created in influences the overall process so that although the basics can be identified, the presence of chemical "impurities", and substitutions along with structural imperfections create
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When the gemstones are in a rough state, the gemologist studies the external structure; the host rock and mineral association; and natural and polished color. Initially, the stone is identified by its color, refractive index, optical character, specific gravity, and examination of internal
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for synthesizing gems, a fine crushed material is heated at extremely high temperatures. The powdered gem mineral is then melted (or a metallic mixture directly burned in an oxygen flame) the residue of which then drips through a furnace onto a boule. The boule where the
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One test to determine the gem's identity is to measure the refraction of light in the gem. Essentially, when light passes from one medium to another, it bends. Blue light bends more than red light. How much the light bends will vary depending on the gem mineral.
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Gemologists study these factors while valuing or appraising cut and polished gemstones. Gemological microscopic study of the internal structure is used to determine whether a gem is synthetic or natural by revealing natural
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is employed to analyze the selective absorption of light in the gem material. Coloring agents or chromophores show bands in the spectroscope and indicate which element is responsible for the gem's color.
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The spectroscopic analysis of cut gemstones also allows a gemologist to understand the atomic structure and identify its origin, which is a major factor in valuing a gemstone. For example, a
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publishes original research articles on all aspects of gemmology, including natural stones and their treatments, synthetics and simulated gemstones. The
Journal is currently published by
317:, also known as relative density, varies depending upon the chemical composition and crystal structure type. Heavy liquids with a known specific gravity are used to test loose gemstones.
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Gemologists use a variety of tools and equipment which allow for the accurate tests to be performed in order to identify a gemstone by its specific characteristics and properties.
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A selection of ornamental, non-precious stones made by tumbling rough pebbles with abrasive grit in a rotating drum. The biggest pebble here is 40 millimetres (1.6 in) long.
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cools down and crystallizes, spins and thus causes the curved striations, which are diagnostic for a lab-created gem: Natural corundum does not show curved striations.
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Gem identification is basically a process of elimination. Gemstones of similar color undergo non-destructive optical testing until there is only one possible identity.
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glass. Synthetics made by the
Verneuil process either do not show flaws at all, or if any flaws are present, show curvy, undulating surfaces rather than flat ones.
302:, above which point light is reflected back internally. This can be measured and thus used to determine the gem's identity. Typically this is measured using a
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travel labs even have their own current supply, which makes them independent from infrastructure. They are also suitable for gemological expeditions.
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is 5.6–5.9 . So one can easily tell the difference between cubic zirconia and the other two; however, there is overlap between ruby and glass.
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The curvature observed in this synthetic color-change sapphire is due to a process known as the
Verneuil process or, flame fusion.
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can help gemologists to determine whether or not a gemstone is natural, synthetic or treated (i.e. fracture-filled or heated).
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equipment and experience to identify the new challenges – such as treatments to gems, new synthetics, and other new materials.
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89:. There are now several professional schools and associations of gemologists and certification programs around the world.
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Specific gravity is measured by comparing the weight of the gem in air with the weight of the gem suspended in water.
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74:(also known as Gem-A), now an educational charity and accredited awarding body with its courses taught worldwide.
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61:(and many non-jewelers) are academically trained gemologists and are qualified to identify and evaluate gems.
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from
Myanmar (Burma) will have definite internal and optical activity variance from a Thai ruby.
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works to separate white light into its component colors. A gemological
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Any single test is nearly always only indicative. For example: The
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121:. The physical property of "hardness" is defined by the irregular
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639:. Photius Coutsoukis and Information Technology Associates. 2003
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crystals that are evidence of heat treatment to enhance color.
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The first US graduate of Gem-A's diploma course, in 1929, was
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Science dealing with natural and artificial gemstone materials
306:, although it is possible to measure it using a microscope.
729:
34:
Examining a pink sapphire under a gemmological microscope
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materials. It is a specific interdisciplinary branch of
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Institutes, laboratories, schools, and publications
105:Gemstones are basically categorized based on their
328:This method uses a similar principle to how a
349:Three inclusion phases in rock crystal quartz
8:
760:Gemmological Association of Great Britain
687:Gemmological Association of Great Britain
601:Gemmological Association of Great Britain
444:Gemmological Association of Great Britain
72:Gemmological Association of Great Britain
544:Professional gemstone testing laboratory
117:, and other optical properties, such as
624:
589:
414:Asian Institute of Gemological Sciences
388:Likewise, natural stones, particularly
360:Identification by flaws and striations
438:Gemmological Association of Australia
148:characteristics under magnification.
7:
49:dealing with natural and artificial
474:International Gemological Institute
603:(Gem-A) in collaboration with the
556:Universal Gemological Laboratories
538:Laboratoire français de gemmologie
495:Center of Gemological of Indonesia
310:Identification by specific gravity
290:Traditional handheld refractometer
282:Identification by refractive index
25:
637:Dictionary of occupational titles
609:American Gemological Laboratories
520:American Gemological Laboratories
432:Gemological Science International
420:Canadian Gemmological Association
81:, who later established both the
462:International School of Gemology
450:Gemological Institute of America
83:Gemological Institute of America
550:Himalaya gem testing laboratory
526:European Gemological Laboratory
514:Advanced Gem Testing Laboratory
489:Gemmological Institute of India
456:Institut National de Gemmologie
426:Canadian Institute of Gemmology
163:Gemmological travel lab KA52KRS
485:Institute of Gem Trading – IGT
480:Italian Gemmological Institute
324:Identification by spectroscopy
243:General identification of gems
123:Mohs scale of mineral hardness
1:
658:"An introduction to gemology"
607:(SSEF) and with support from
605:Swiss Gemmological Institute
501:Swiss Gemmological Institute
341:Identification by inclusions
818:
755:"The Journal of Gemmology"
730:"Institute of Gem Trading"
708:. Butterworth-Heinemann.
662:International Gem Society
792:Gemological laboratories
734:Institute of Gem Trading
597:The Journal of Gemmology
570:The Journal of Gemmology
702:Read, Peter G. (2005).
508:Commercial laboratories
193:Contact liquid for RI (
152:Gemological instruments
468:Hoge Raad voor Diamant
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350:
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35:
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298:Every material has a
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220:(handheld or desktop)
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33:
764:(subscription page).
408:American Gem Society
133:or partially melted
87:American Gem Society
577:Gems & Gemology
207:Optic figure sphere
190:Magnifying eyepiece
802:Types of jewellery
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351:
292:
270:is 3.15–4.20, and
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186:Polarising filter
107:crystal structure
16:(Redirected from
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374:Verneuil process
315:Specific gravity
260:specific gravity
238:Ultraviolet lamp
195:refractive index
131:fluid inclusions
115:refractive index
111:specific gravity
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532:Gübelin Gem Lab
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278:"individuals".
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167:These include:
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272:cubic zirconia
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171:Corrected 10×
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79:Robert Shipley
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304:refractometer
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738:. Retrieved
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665:. Retrieved
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641:. Retrieved
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633:"Gemologist"
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563:Publications
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371:
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334:spectroscope
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232:Color filter
218:Spectroscope
197:) up to 1.81
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100:
91:
76:
68:
42:
38:
37:
372:During the
229:Stone cloth
213:Dichroscope
203:Polariscope
119:pleochroism
787:Mineralogy
776:Categories
740:2019-10-13
736:. Thailand
667:2017-08-28
643:2009-11-08
619:References
402:Institutes
354:Inclusions
177:Microscope
97:Background
55:mineralogy
797:Jewellery
705:Gemmology
682:"History"
584:Footnotes
266:is 4.00,
135:exogenous
43:gemmology
18:Gemmology
782:Gemology
379:corundum
226:Tweezers
223:Penlight
85:and the
59:jewelers
51:gemstone
39:Gemology
762:(Gem-A)
689:(Gem-A)
446:– Gem-A
65:History
57:. Some
47:science
45:is the
712:
611:(AGL).
552:– HGTL
546:– PGTL
516:– AGTL
503:– SSEF
416:– AIGS
383:spinel
558:– GCI
540:– LFG
534:– GGL
528:– EGL
522:– AGL
497:– COG
491:– GII
482:– IGI
476:– IGI
470:– HRD
464:– ISG
458:– ING
452:– GIA
440:– GAA
434:– GSI
428:– CIG
422:– CGA
410:– AGS
390:beryl
330:prism
268:glass
173:loupe
710:ISBN
264:ruby
142:ruby
381:or
262:of
41:or
778::
757:.
732:.
684:.
660:.
635:.
125:.
113:,
109:,
743:.
718:.
691:.
670:.
646:.
20:)
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
