Iran formally known as Persia remains the most significant source of turquoise for over 2000 years. Turquoise was used to decorate mosques, turbans and brides and today is used to make beautiful turquoise rings, necklaces, bracelets and earrings. The Aztecs used inlaid turquoise with gold, quartz, malachite, jade, coral and shells in ceremonial mosaic objects and masks. Egyptians used turquoise as far back as Tutankhamun’s Tomb decorating the burial mask with inlaid turquoise. It was widely used in Egyptian Revival pieces c.1820. Today, turquoise mines can be found in Arizona, California, New Mexico and Nevada. New Mexico has the oldest mine. Although the mines are mostly depleted today, they were very productive before the 1920’s. Arizona is now the largest producer of turquoise followed closely by Nevada which has 120 mines. China is a minor source of turquoise. Turquoise is judged in three areas color, texture and presence or absence of matrix. Color The most valuable is an intense to medium blue coming from Iran known as Persian turquoise. American and Mexican shades ranging from light blue to yellow green are also considered valuable. Splotches of white or green in a blue stone make it less valuable than a blue stone. Iron deposits cause turquoise to appear a greenish blue color while copper creates the most valuable blue color. Texture The texture of turquoise is made up of cryptocrystalline. When these crystals form close together it creates the finest turquoise which is less porous and has a finer texture. Porosity affects durability. Turquoise is a softer stone with hardest being a 5 or 6 on the Mohrs scale. Matrix The turquoise deposits form in limonite and sandstone creating either brown or tan markings. When looking for your special turquoise ring or jewelry item look for the pretty blue shade without any matrix. It is not as often seen but is worth the search.