Tourmaline is a crystalline boron silicate mineral compounded with elements such as aluminium, iron, magnesium, sodium, lithium, or potassium. Tourmaline is classified as a semi-precious stone and the gemstone comes in a wide variety of colors. The name comes from the Tamil and Sinhalese word "Turmali or "Thoramalli, which applied to different gemstones found in Sri Lanka. Tourmaline is a six-member ring cyclosilicate having a trigonal crystal system.It occurs as long, slender to thick prismatic and columnar crystals that are usually triangular in cross-section, often with curved striated faces. The style of termination at the ends of crystals is sometimes asymmetrical, called hemimorphism. Small slender prismatic crystals are common in a fine-grained granite called Aplite, often forming radial daisy-like patterns. Tourmaline is distinguished by its three-sided prisms; no other common mineral has three sides. Prisms faces often have heavy vertical striations that produce a rounded triangular effect. All hemimorphic crystals are piezoelectric, and are often pyroelectric as well. Tourmaline is found in a variety of colors.
The most common variety, known as Schorl, is black. Usually, iron-rich tourmalines are black to bluish-black to deep brown, while magnesium-rich varieties are brown to yellow, and lithium-rich tourmalines are almost any color: blue, green, red, yellow, pink, etc. Bi-colored and multicolored crystals are common, reflecting variations of fluid chemistry during crystallization. However, finding well-terminated crystals of sufficient length to show the multi-colored layers without damage is difficult.Crystals may be green at one end and pink at the other, or green on the outside and pink inside; this type is called "Watermelon" Tourmaline. Some forms of tourmaline are dichroic, in that they change color when viewed from different directions. On offer here is a version of a "Watermelon" Tourmaline. It is rare due to: 1 its size (10.37 carats); 2 its clarity/transparency (inclusions are loupe-visible or under 20x magnification in photos near the color junction) and 3 the quality of its colors of blue and pink. This gem measures 12.12 x 11.73 x 8.59 mm and weighs 10.37 carats. The inclusions are clustered in the middle of the gem, seen most clearly from the photos taken proximate to the color dividing line. The stone has an emerald cut. The final photo in the series is a scan of the American Gemological Laboratory (AGL) Tourmaline BriefT certifying its authenticity. This item is in the category "Jewelry & Watches\Loose Diamonds & Gemstones\Loose Gemstones". The seller is "naturesgems2000" and is located in this country: US. This item can be shipped to United States, Canada, United Kingdom, Denmark, Romania, Slovakia, Bulgaria, Czech Republic, Finland, Hungary, Latvia, Lithuania, Malta, Estonia, Australia, Greece, Portugal, Cyprus, Slovenia, Japan, China, Sweden, Korea, South, Indonesia, Taiwan, South Africa, Thailand, Belgium, France, Hong Kong, Ireland, Netherlands, Poland, Spain, Italy, Germany, Austria, Bahamas, Israel, Mexico, New Zealand, Singapore, Norway, United Arab Emirates, Qatar, Kuwait, Bahrain, Croatia, Republic of, Malaysia, Chile, Colombia, Barbados, Bangladesh, Bermuda, Brunei Darussalam, Bolivia, Egypt, French Guiana, Guernsey, Gibraltar, Guadeloupe, Iceland, Jersey, Jordan, Cambodia, Cayman Islands, Liechtenstein, Sri Lanka, Luxembourg, Monaco, Macau, Martinique, Maldives, Nicaragua, Oman, Pakistan, Paraguay, Reunion, Uruguay.