Gem De Che
Group of precious and semiprecious stones—both uncut and faceted—including ( clockwise from top left), uncut synthetic, uncut, and crystal cluster. A gemstone (also called a gem, fine gem, jewel, precious stone, or semi-precious stone) is a piece of mineral which, in cut and polished form, is used to make or other. However, certain (such as and ) and occasionally materials that are not minerals (such as, and ) are also used for jewelry and are therefore often considered to be gemstones as well. Most gemstones are hard, but some soft minerals are used in jewelry because of their or other physical properties that have. Rarity is another characteristic that lends value to a gemstone. Apart from jewelry, from earliest antiquity and, such as cups, were major luxury art forms.
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A gem maker is called a or; a cutter is called a. A selection of gemstone pebbles made by tumbling rough rock with abrasive grit, in a rotating drum. The biggest pebble here is 40 mm (1.6 in) long. The traditional classification in the West, which goes back to the, begins with a distinction between precious and semi-precious; similar distinctions are made in other cultures. In modern use the precious stones are, and, with all other gemstones being semi-precious. This distinction reflects the rarity of the respective stones in ancient times, as well as their quality: all are with fine color in their purest forms, except for the colorless diamond, and very hard, with hardnesses of 8 to 10 on the. Other stones are classified by their color, and hardness.
The traditional distinction does not necessarily reflect modern values, for example, while are relatively inexpensive, a green garnet called can be far more valuable than a mid-quality emerald. Another unscientific term for semi-precious gemstones used in and is.
Use of the terms 'precious' and 'semi-precious' in a commercial context is, arguably, misleading in that it deceptively implies certain stones are intrinsically more valuable than others, which is not necessarily the case. In modern times gemstones are identified by, who describe gems and their characteristics using specific to the field of. The first characteristic a gemologist uses to identify a gemstone is its. For example, are made of (C) and rubies of ( Al 2O 3). Next, many gems are crystals which are classified by their such as. Another term used is, the form the gem is usually found in.
For example, diamonds, which have a cubic crystal system, are often found as. Gemstones are classified into different groups, species, and varieties.
For example, ruby is the red variety of the species, while any other color of corundum is considered sapphire. Other examples are the emerald (green), (blue), (red), (colorless), (yellow) and (pink), which are all varieties of the mineral species. Gems are characterized in terms of, and luster. They may exhibit.
They may have and a distinctive. Material or flaws within a stone may be present as.
Gemstones may also be classified in terms of their 'water'. This is a recognized grading of the gem's luster, transparency, or 'brilliance'. Very transparent gems are considered ', while 'second' or 'third water' gems are those of a lesser transparency. A diamond cutter in in the in 2012 A few gemstones are used as gems in the crystal or other form in which they are found. Most however, are cut and polished for usage as jewelry. The picture to the left is of a rural, commercial cutting operation in Thailand.
This small factory cuts thousands of carats of sapphire annually. The two main classifications are stones cut as smooth, dome shaped stones called, and stones which are cut with a by polishing small flat windows called at regular intervals at exact angles. Stones which are opaque or semi-opaque such as, 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. Gems which are transparent are normally faceted, a method which shows the optical properties of the stone's interior to its best advantage by maximizing reflected light which is perceived by the viewer as sparkle.
There are many commonly used shapes for. The facets must be cut at the proper angles, which varies depending on the properties of the gem. If the angles are too steep or too shallow, the light will pass through and not be reflected back toward the viewer.
The faceting machine is used to hold the stone onto a flat lap for cutting and polishing the flat facets. Rarely, some cutters use special curved laps to cut and polish curved facets.
Nearly 300 variations of diamond color exhibited at at the Natural History Museum in London. The color of any material is due to the nature of light itself. Daylight, often called white light, is actually 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. A material which is mostly the same can exhibit different colors.
For example, ruby and sapphire have the same primary chemical composition (both are ) but exhibit different colors because of impurities. Even the same named gemstone can occur in many different colors: sapphires show different shades of blue and pink and 'fancy sapphires' exhibit a whole range of other colors from yellow to orange-pink, the latter called '. 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 are sufficient to absorb certain colors and leave the other colors unaffected. For example, which is colorless in its pure mineral form, becomes emerald with chromium impurities. If is added instead of, beryl becomes pink. With iron, it becomes.
Some gemstone treatments make use of the fact that these impurities can be 'manipulated', thus changing the color of the gem. Treatment Gemstones are often treated to enhance the color or clarity of the stone.
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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. Heat Heat can improve gemstone color or clarity. The heating process has been well known to gem miners and cutters for centuries, and in many stone types heating is a common practice. Most is made by heating, and partial heating with a strong gradient results in “” – a stone partly amethyst and partly citrine. Is often heated to remove yellow tones, or to change green colors into the more desirable blue, or enhance its existing blue color to a purer blue. Nearly all is heated at low temperatures to remove brown undertones and give a more desirable blue / purple color.
A considerable portion of all and is treated with a variety of heat treatments to improve both color and clarity. When jewelry containing diamonds is heated (for repairs) the diamond should be protected with; otherwise the diamond (which is pure carbon) could be burned on the surface or even burned completely up.
When jewelry containing or is heated, those stones should not be coated with boracic acid (which can etch the surface) or any other substance. They do not have to be protected from burning, like a diamond (although the stones do need to be protected from heat stress fracture by immersing the part of the jewelry with stones in water when metal parts are heated). Radiation. 2007-06-05 at the. And 2007-06-03 at the. Alden, Nancy (2009).
New York, NY:., Max Bauer, p. W., 2006, Secrets Of The Gem Trade, The Connoisseur's Guide To Precious Gemstones, Brunswick House Pr, pp. 3–8. ^ Frangoulis, George (18 April 2015). AskOxford.com Concise Oxford English dictionary online.
Desirable diamonds: The world's most famous gem. By Sarah Todd. W., 2006, Secrets of The Gem Trade, The Connoisseur's Guide To Precious Gemstones, Brunswick House Pr, p.36. Wise, R. W., 2006, Secrets Of The Gem Trade, The Connoisseur's Guide To Precious Gemstones, Brunswick House Pr, p. 15. Burnham, S.M.
Precious Stones in Nature, Art and Literature. Bradlee Whidden. Page 251 URL: 2010-10-13 at the. Church, A.H. (Professor at Royal Academy of Arts in London) (1905). Precious Stones considered in their scientific and artistic relations.
His Majesty's Stationery Office, Wyman & Sons. Chapter 1, Page 9: Definition of Precious Stones URL: 2007-09-29 at the. ^ Secrets of the Gem Trade; The Connoisseur's Guide to Precious Gemstones, Richard W Wise, Brunswick House Press, Lenox, Massachusetts., 2003. 'HowStuffWorks'.
From the original on 2014-11-06. Retrieved 2014-11-06. Monthly, Jewellery (2015-04-02). Jewellery & Watch Magazine Jewellery news, jewellery fashion and trends, jewellery designer reviews, jewellery education, opinions Wrist watch reviews - Jewellery Monthly.
From the original on 2017-08-28. Retrieved 2017-08-28.
Gem De Che Phong Thu
'Artificial treatment of gemstones'. Dictionary of Gems and Gemology. Berlin, Heidelberg: Springer Berlin Heidelberg. From the original on 2011-07-26. Retrieved 2010-07-30. Introduction to Lapidary by Pansy D. Kraus.
Faceting For Amateurs by Glen and Martha Vargas. The Natural Sapphire Company Blog. Retrieved 2018-01-19.
Tai Game De Che
Gemstone Enhancement: History, Science and State of the Art by Kurt Nassau. Nassau, Kurt (1994). Gem Enhancements. Butterworth Heineman. 2016-06-20 at the. Chilton Company.
Carnegie Institution for Science. From the original on 1 December 2010. Retrieved 7 January 2011. Folkard, Claire; Freshfield, Jackie; Masson, Carla; Dimery, Rob (12 December 2017). Guinness World Records Limited. External links Wikiquote has quotations related to: Wikimedia Commons has media related to.
Gem De Che
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