Stones which are opaque or semi-opaque such as opal, turquoise, variscite, etc. are commonly cut as cabochons. These gems are designed to show the stone's color or surface properties as in opal and star sapphires. Grinding wheels and polishing agents are used to grind, shape and polish the smooth dome shape of the stones. [24] a b Li, Zhaolin (December 1, 2001). "Study on inclusions in natural and synthetic gems". Chinese Journal of Geochemistry. 20 (4): 324–332. doi: 10.1007/BF03166857. ISSN 1993-0364. S2CID 129031255. The Gem and Jewelry Institute of Thailand (Public Organization) or GIT, Thailand's national institute for gemological research and gem testing, Bangkok [21]

List of Gemstones: Precious and Semi-Precious Stones - Gem

Institute for Gems and Gold Research of VINAGEMS (Vietnam), founded by Dr. Van Long Pham [ citation needed] This difference in color is based on the atomic structure of the stone. Although the different stones formally have the same chemical composition and structure, they are not exactly the same. Every now and then an atom is replaced by a completely different atom, sometimes as few as one in a million atoms. These so-called impurities are sufficient to absorb certain colors and leave the other colors unaffected. Rapaport report of ICA Gemstone Conference in Dubai". Diamonds.net. May 16, 2007. Archived from the original on July 26, 2011 . Retrieved July 30, 2010.

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Prior to development of synthesising processes the alternatives on the market to natural gemstones were imitations or fake. It was in 1837 that the first successful synthesis of ruby occurred. [43] French chemist Marc Gaudin managed to produce small crystals of ruby from melting together potassium aluminium sulphate and potassium chromate through what would later be known as the flux melt process. [44] Following this, another French chemist Fremy was able to grow large quantities of small ruby crystals using a lead flux. [45]

List of gemstones by species - Wikipedia List of gemstones by species - Wikipedia

A few years later an alternative to flux melt was developed which led to the introduction of what was labeled "reconstructed ruby" to the market. Reconstructed ruby was sold as a process which produced larger rubies from melting together bits of natural ruby. [46] In later attempts to recreate this process it was found to not be possible and is believed reconstructed rubies were most likely created using a multi-step method of melting of ruby powder. [44] Shigley, James (2000). "Treated and synthetic gem materials". Current Science. 79 (11): 1566–1571. JSTOR 24104849. Synthetic gemstones share chemical and physical properties with natural gemstones but there are some slight differences that can be used to discern synthetic from real. [47] These differences are slight and often require microscopy as a tool to distinguish differences. Undetectable synthetics pose a threat to the market if they are able to be sold as real rare gemstones. Because of this there are certain characteristic gemologists look for. Each crystal is characteristic to the environment and growth process under which it was created.

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Flame fusion process was the first process used which successfully created large quantities of synthetic gemstones to be sold on the market. [43] This remains the most cost effective and common method of creating corundums today. Cultured, synthetic, or "lab-created" gemstones are not imitations: The bulk mineral and trace coloring elements are the same in both. For example, diamonds, rubies, sapphires, and emeralds have been manufactured in labs that possess chemical and physical characteristics identical to the naturally occurring variety. Synthetic (lab created) corundum, including ruby and sapphire, is very common and costs much less than the natural stones. Small synthetic diamonds have been manufactured in large quantities as industrial abrasives, although larger gem-quality synthetic diamonds are becoming available in multiple carats. [37]

Gemstones of the World: Newly Revised Fifth Edition

a b "10 Gems Rarer and More Valuable Than Diamonds". The Spruce Crafts. Archived from the original on March 31, 2023 . Retrieved March 31, 2023. Padparadscha Sapphires: 10 Tips On Judging The Rare Gem". The Natural Sapphire Company Blog. April 6, 2015. Archived from the original on January 19, 2018 . Retrieved January 19, 2018. To produce corundum, a pure aluminium powder is used with different additives to achieve different colors. [44]Red beryl or bixbite was discovered in an area near Beaver, Utah in 1904 and named after the American mineralogist Maynard Bixby. Virtually all blue topaz, both the lighter and the darker blue shades such as "London" blue, has been irradiated to change the color from white to blue. Most green quartz (Oro Verde) are also irradiated to achieve the yellow-green color. Diamonds are mainly irradiated to become blue-green or green, although other colors are possible. When light-to-medium-yellow diamonds are treated with gamma rays they may become green; with a high-energy electron beam, blue. [35] Waxing/oiling [ edit ] The book begins with descriptions of gemstone identification properties. Moh’s scale of hardness, basic mineral chemistry, specific gravity, cleavage and fracture, refraction and absorption, pleochroism, and fluorescence are described in sections followed by charts of these properties for selected gemstones. Later, these concepts are referenced and quantified in specific descriptions for each gemstone. Short, useful sections on mining, polishing, and faceting follow. Gemstones are often treated to enhance the color or clarity of the stone. In some cases, the treatment applied to the gemstone can also increase its durability. Even though natural gemstones can be transformed using the traditional method of cutting and polishing, other treatment options allow the stone's appearance to be enhanced. [27] Depending on the type and extent of treatment, they can affect the value of the stone. Some treatments are used widely because the resulting gem is stable, while others are not accepted most commonly because the gem color is unstable and may revert to the original tone. [28] Early history [ edit ]

Gemstones of the world : Schumann, Walter : Free Download Gemstones of the world : Schumann, Walter : Free Download

Artificial treatment of gemstones". Dictionary of Gems and Gemology. Berlin, Heidelberg: Springer Berlin Heidelberg. 2009. pp. 50. doi: 10.1007/978-3-540-72816-0_1308. ISBN 9783540727958. The color of any material is due to the nature of light itself. Daylight, often called white light, is all of the colors of the spectrum combined. When light strikes a material, most of the light is absorbed while a smaller amount of a particular frequency or wavelength is reflected. The part that is reflected reaches the eye as the perceived color. A ruby appears red because it absorbs all the other colors of white light while reflecting the red.

Taaffeite was discovered in 1945. It was named after the discoverer, the Irish gemologist Count Edward Charles Richard Taaffe.