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Gems also called gem minerals are a subgroup of minerals and only Essay

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Gems, also called gem minerals, are a subgroup of minerals, and only 0.001% of the known minerals are considered to be gems. Of these, only one of ten is considered valuable enough to be important gemstone on the world market. The value of a gem is determined by its rarity, durability, and aesthetic quality.The aesthetics of a gem is determined by its natural clarity, brilliance, and colour, which can be enhanced by the way it is cut. There are two main types of cuts.

The faceted cut, which has numerous flat cut surfaces or facets with a round, oval, square, rectangular, or pear-shaped overall shape, are generally preferred for brilliant transparent stones such as diamond. The cabochon cut, the other way of cutting, has a smooth rounded top, usually with a flat base, and is mainly used for opaque or translucent stones.The hardness of a mineral is measured using Mohs’ Scale, a scale ranging from 1 to 10, where 10 is the hardest.

In order to be considered a gem, the mineral should have a Mohs’ hardness of 6 or more, and 7 to be considered a comparatively durable gem. The tables show some of the common minerals, their chemical composition, and hardness.The significance of a gemstone depends on its beauty, rarity, and size. These factors are directly proportionate to the value. The size is measured in carats, where a carat is 0.2 grams. A single carat is further subdivided into points, specifically 100 points making one carat.There are three categories gems, depending on their origin; whether they are mined, synthetically made, or obtained from organic materials.A synthetic gem is one made in a laboratory but possesses the same chemical, physical, and optical characteristics as the natural equivalent, unless additional components are added on purpose to increase aesthetics or durability. Due to the difficulty in differentiating between natural and synthetic gems, the Federal Trade Commission (or its equivalent for other countries) has put into place strict guidelines regarding how they are marketed or sold, mainly that synthetic gems are to be described in a way that leaves no doubt that it was not produced naturally, as synthetic gems have a much lower worth.Synthetic gems originated from the late 1800s, and the first successful production was a ruby of faceting quality. The production of synthetic gems emerged due to the high demand for the durable stones in industrial applications outside the jewellery industry.For the past century, from the few and far between new manmade minerals marketed, it can be concluded that the repertoire of synthetic gems is reaching its limit. However, the ways to manufacture these gems are not limited, though these methods typically fall into two categories: melt or solution. Depending on the different types of gems, different methods of synthetic production are favoured.During melt processes, constituents of the gem in mind are added and melted, such that the chemical composition of the resulting melt is the same as the composition of the resulting crystal, hence forming the gem when it solidifies. In solution processes, however, the constituents are dissolved in a solution at high temperature, and the crystal forms on a seed crystal as the temperature is lowered.Melt processes include the Flame Fusion or Verneuil Process.The flame fusion process produced the first commercially successful synthetic gems. This process involves dropping powdered chemicals through a high-temperature flame, where it melts and falls onto a rotating pedestal to produce a synthetic crystal. This process is the least expensive and most common way to make gems such as synthetic corundum and spinel.The Crystal Pulling or Czochralski Process is another melt process. The pulling process emerged in the early 1900s. In this process, nutrients are melted in a crucible and the synthetic crystal grows from a seed that is dipped into the melt, and then slowly pulled away from the melt as it grows. Gems synthesized by pulling include synthetic alexandrite, chrysoberyl, corundum, and garnet.The Flux Growth is a solution process and is used to create a large number of synthetic gems, such as diamond, emerald, ruby, sapphire, alexandrite, and spinel. Flux is a solid material that, when melted, dissolves other materials in the same way that water dissolves sugar. As the dissolved chemical solution gradually cools, synthetic crystals form. This process requires patience and significant investment, as crystal growth can take up to a year, and the equipment is very expensive.Hydrothermal Growth is a solution process. Like the flux process, the hydrothermal growth process is slow and expensive. However, it is the only method for successfully growing synthetic quartz. This process requires heat and pressure and imitates the conditions deep in the earth that result in the formation of natural gems. Nutrients are dissolved in a water solution, and synthetic crystals are formed as the solution cools.Organic gems come from living material and include pearls, amber, coral, ivory, and jet.Pearls are spheres of calcium carbonate formed within molluscs due to some form of irritation, the most common being grains of sand. Pearls are commonly in shades of white, but some have bluish, pinkish, or even dark grey tints.Amber fossilized tree resin that hardened over millions of years. Amber is normally yellow-brown in colour, but other shades vary drastically from almost white to almost black. Common ambers are completely clear, and those that contain inclusions of insects or other matter are considered more desirable. Amber is known for the special property of being able to become charged through friction.Coral, similar to pearls, is also mainly calcium carbonate and is derived from the outer shells of small marine animals. Coral exists in an array of colours, but the greatest demand is for the rarest red coral.Ivory is a bonelike material that comes from the tusks of animals including elephants, walruses, and hippopotamuses. The hunt for ivory is the drive for most if not all cases of poaching. The pale cream colour of new ivory becomes turns yellow with age, and it does not peel, although it is brittle.Jet is condensed or densified lignite coal, or fossilized plant material, from millions of years. Jet is mainly from England, where it is derived from fossil driftwood buried under the sea. However, it has a drawback as a gemstone, specifically its flammable tendency, since it is literally highly polished coal. 6 Chemistry Interest GroupOrganic Gems and their Applicationsby Chen Yanlin—Џ—Џ—Џ—Џ—Џ—Џ—Џ—Џ—Џ—Џ—Џ—Џ—Џ—Џ—Џ—Џ—Џ—Џ—Џ—Џ—Џ—Џ—Џ—Џ—Џ—Џ—Џ—Џ—Џ—Џ—Џ—Џ—Џ—Џ—Џ—Џ—ЏGemstones have a wide range of uses, and the importance and admiration of some of the harder gemstones such as sapphire, diamond and ruby go far beyond their aesthetic beauty or mythical powers, with many of these gems having a vital role in industry and modern technology.Diamond has a Mohs’ hardness of 10, with an incredible tolerance to heat and a durability that makes it literally indestructible. Its hardness and resilience give it high regard in many industries and can be used for high powered lasers (focusing extremely accurate rays of light), drilling, cutting (diamond tip or teeth, respectively), and polishing (diamond powder).Sapphires are used as a key part in various machines, technologies and industrial processes, including complex circuit boards and high-frequency lasers. Sapphire has the ability to form electrical insulations without the risk of overheating, making it perfect for technologies which demand high heat conductivity and low electrical conductivity. Sapphires can also be made into sapphire glass, known for its strength, durability and resistance to scratches. Windows made of sapphire glass can be found in military vehicles or in high pressured chambers.Ruby was historically known for being used in the first lasers. Ruby continues to be used in lasers today and produces the common red-light laser beams seen in supermarket scanners and laser pointers. Ruby has a Mohs’ hardness of nine, and its hardness allows it to play a part in the mechanics of certain clocks and machine parts which need great durability.Since the use of gems in industrial processes only requires the physical properties of gemstones, the usage is more often than not synthetically produced gems, instead of natural ones.

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