Top 10 most Valuable gemstone rock type gems in the World !!! More: http://j.gs/8D5f Source link : http://j.gs/8D5f "Gem" and "Jewels" redirect here. For other uses, see Gem (disambiguation) and Jewels (disambiguation). "Precious Stone" redirects here. For the James Bond character, see Hurricane Gold. For other uses, see Gemstone (disambiguation). Group of precious and semiprecious stones —both uncut and faceted— including (clockwise from top left) diamond, uncut synthetic sapphire, ruby, uncut emerald, and amethyst crystal cluster. A gemstone (also called a gem, fine gem, jewel, precious stone or semi-precious stone) is a piece of mineral crystal which, in cut and polished form, is used to make jewelry or other adornments.[1][2] However, certain rocks (such as lapis lazuli) or organic materials that are not minerals (such as amber or jet) 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 luster or other physical properties that have aesthetic value. Rarity is another characteristic that lends value to a gemstone. Apart from jewelry, from earliest antiquity engraved gems and hardstone carvings, such as cups, were major luxury art forms. A gem maker is called a lapidary or gemcutter; a diamond worker is a diamantaire. The carvings of Carl Fabergé are significant works in this tradition. The traditional classification in the West, which goes back to the ancient Greeks, begins with a distinction between precious and semi-precious; similar distinctions are made in other cultures. In modern usage the precious stones are diamond, ruby, sapphire, and emerald, with all other gemstones being semi-precious.[3] This distinction reflects the rarity of the respective stones in ancient times, as well as their quality: all are translucent with fine color in their purest forms, except for the colorless diamond, and very hard, with hardnesses of 8 to 10 on the Mohs scale. Other stones are classified by their color, translucency and hardness. The traditional distinction does not necessarily reflect modern values, for example, while garnets are relatively inexpensive, a green garnet called tsavorite can be far more valuable than a mid-quality emerald.[4] Another unscientific term for semi-precious gemstones used in art history and archaeology is hardstone. 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 gemologists, who describe gems and their characteristics using technical terminology specific to the field of gemology. The first characteristic a gemologist uses to identify a gemstone is its chemical composition. For example, diamonds are made of carbon (C) and rubies of aluminium oxide (Al 2O 3). Next, many gems are crystals which are classified by their crystal system such as cubic or trigonal or monoclinic. Another term used is habit, the form the gem is usually found in. For example, diamonds, which have a cubic crystal system, are often found as octahedrons. Gemstones are classified into different groups, species, and varieties. For example, ruby is the red variety of the species corundum, while any other color of corundum is considered sapphire. Other examples are the Emerald (green), aquamarine (blue), red beryl (red), goshenite (colorless), heliodor (yellow), and morganite (pink), which are all varieties of the mineral species beryl. Gems are characterized in terms of refractive index, dispersion, specific gravity, hardness, cleavage, fracture, and luster. They may exhibit pleochroism or double refraction. They may have luminescence and a distinctive absorption spectrum. Historically, all gemstones were graded using the naked eye. The GIA system included a major innovation: the introduction of 10x magnification as the standard for grading clarity. Other gemstones are still graded using the naked eye (assuming 20/20 vision).[7]source:https://en.wikipedia.org/wiki/Gemstone Top 10 most Valuable gemstone rock type gems in the World !!! More Videos: 10-Minute Home Circuit Workout | Total Body Strength Workout https://www.youtube.com/watch?v=RJ5Mh8-Y360 5 Surprising Foods for Healthy Teeth / healthy teeth foods https://www.youtube.com/watch?v=eDAdMXEOyBk 8 Ways To Improve Your Fitness level !!!! The Test of Fitness 2016/2017 https://www.youtube.com/watch?v=42DydImNjDk 7 Smart Ways to Reduce Thanksgiving Foods and Take nutrition https://www.youtube.com/watch?v=Q5365cbWC_4 Top 10 Thanksgiving Problems Solved !! https://www.youtube.com/watch?v=OtyUllIda4c

• published: 26 Nov 2016
• views: 588