Turquoise is the birthstone of December & anniversary gemstone for the 11th year of marriage. Turquoise is a valuable mineral and is possibly the most valuable, non-transparent mineral in the jewelry trade.The finest turquoise comes from Iran but is challenged by some southwestern United States specimens. Turquoise is often imitated by "fakes", such as the mineral chrysocolla, and poorer turquoise specimens are often dyed or color stabilized with coatings of various resins. The name comes from a french word which means stone of Turkey, from where Persian material passed on its way to Europe. Usually found in association with copper deposits, turquoise is sometimes collected as a by-product of copper mining. Turquoise occurs as nodules and veins that are either blue or green in color. The mineral is composed of hydrated copper and aluminum phosphate and is a secondary mineral deposited from circulating waters. It occurs chiefly in arid environments as blue to greenish, waxy veinlets in aluminum-rich, weathered, volcanic, or sedimentary rocks.You may find its physical characteristics: · Color is of course, turquoise, but this color actually varies from greenish blue to sky blue shades. · Luster is dull to waxy, vitreous in macro-crystals. · Transparency specimens are opaque. · Crystal System is triclinic; bar 1 · Crystal Habits include crystals rarely large enough to see, usually massive, cryptocrystalline forms as nodules and veinlets. · Cleavage is perfect in two direction, but is not often seen. · Fracture is conchoidal and smooth. · Hardness is 5 - 6 ·· Specific Gravity is approximately 2.6 - 2.8 (average) · Streak is white with a greenish tint. · Other Characteristics: color can change with exposure to skin oils. · Best Field Indicators are crystal habit, hardness, luster, color and associations. Chemically, a hydrated phosphate of copper and aluminum, turquoise is formed by the percolation of meteoric or groundwater through aluminous rock in the presence of copper. For this reason, it is often associated with copper deposits as a secondary mineral, most often in copper deposits in arid, semiarid, or desert environments. The most important turquoise deposits are in Iran, Hubei province of China, and the Southwestern United States. Turquoise from Iran is often said to be the best, because it is sometimes a clear sky blue with no green and no black veins running through the stones. The largest turquoise deposits are in the northwest Hubei province of China .Its basic color is green with net vein and the surface is very smooth as while tough structure. From Qing Dynasty, a number of turquoise mines operated in that area, several or more mines in each of the counties.The famous mines is YunGaiSi in Yun county and LaBa Mountain in ZhuShan county. Turquoise is a porous stone and therefore requires special care. Clean with a soft, damp cloth and pat dry. Do not use soap or soak the stones in water. Ultrasonic cleaning processes may also damage the stones. Apply deodorants, cosmetics and fragrances prior to putting on your turquoise jewelry. If exposed to extreme sunlight or heat, turquoise may change colour. Always store it in a cool dry place