| ZOISITE MINERAL FACTS | |
|
| The Gem and Mineral Collector's Photo Gallery by Nevada Outback |
|
. Zoisite Mineral Facts:
Chemical Formula: Ca2Al3(SiO4)(Si2O7)O(OH) Colors: blue to violet, green, brown, pink, yellow, gray, or colorless Hardness: 6 to 6.5 Density: 3.25 to 3.37 Cleavage: The cleavage is perfect parallel to (010).
Crystallography: Orthorhombic Luster:. Vitreous luster. Transparent to nearly opaque. Optics: (Refractive Index): = a= 1.7002, b=1.7025, y=1.7058 |
|
. |
Composition,
Structure and Associated Minerals: The massive rose-red variety, containing manganese as a coloring agent, is known as thulite. Thulite is translucent and sometimes used as a gem stone. It occurs in metamorphic rocks, especially those formed from igneous rocks rich in lime.
Identification and Diagnostics
Occurrence,
Localities and Origins: Good specimen grade crystals of zoisite are found near Pregratten in Tyrol; at Kleppan (thulite), Parish Souland, Norway, and in the ore bearing veins at the copper mines of Ducktown, Tennessee, where it is associated with chalcopyrite, pyrite and quartz. Gem tanzanite comes from a location in the Merelani Hills, near Arusha, Tanzania. The mines are located about 50 miles south of the famous Mt. Kilimanjaro. The world's only economic tanzanite mines take up only a small area, about 1.5 miles wide and less than 5 miles long. This is the nation of Tanzania's most important gem mining area, with as many as 70,000 people living in the area and supported by the mining, cutting and gemstone trade. The area has been subjected to strong regional metamorphic forces. The gem bearing ground is broken up into 4 blocks, A through D. It is said that 5000 to 6000 miners work at Block D (the most productive area). Block D is the area where the deepest shafts are found, as the productive geology trends down from Blocks A through D. The tanzanite is recovered from pegmatitic veins that have become so faulted and stressed they have broken into smaller pieces known as boudins. Gems are found in small pockets within the pegmatite bodies. Only a small portion of the tanzanite crystals are clear enough for gem use. Minerals associated with the tanzanite include calcite, graphite and pyrite. Natural tanzanite often has an orange or brown color element which is removed by gentle heat treatment prior to gem usage. In fact, natural tanzanite often has little or none of the deep blue color it is so famous for. A very small amount of the Merelani tanzanite is colored by Chromium, giving a green color similar to emeralds. These are rarely seen on the market. While Tanzania is the source of nearly all of the gem material, small amounts of gem tanzanite have been found in Kenya. The Kenyan tanzanite is a lighter blue color. For more information on gem Tanzanite, see: Tanzanite - Beautiful Blues Return to the Mineral Collectors Information Page |
|
|
|
|
||
|
|
|
|
|
|
||
Please note that the author, Chris Ralph, retains all copyrights to this entire document and it may not be reproduced, quoted or copied without permission.
NEVADA OUTBACK GEMS TURQUOISE AND JEWELRY
