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Tanzanite is the blue and violet variety of the mineral zoisite (a calcium aluminium hydroxyl sorosilicate), ... Pleochroism in tanzanite
Pleochroism is an extremely useful tool in mineralogy and gemology for mineral and gem identification, since the number of colors visible from different angles can identify the possible crystalline structure of a gemstone or mineral and therefore help to classify it. Minerals that are otherwise very similar often have very different pleochroic ...
Zoisite may be blue to violet, green, brown, pink, yellow, gray, or colorless. Blue crystals are known under the name tanzanite. It has a vitreous luster and a conchoidal to uneven fracture. When euhedral, zoisite crystals are striated parallel to the principal axis (c-axis). Also parallel to the principal axis is one direction of perfect cleavage.
The most currently known example of natural trichroism (rare 3 sided pleochroism) is Tanzanite. Despite some claims to be the only mineral (or gemstone) to exhibit such effect, it is not. However it is often considered to have the strongest trichroic effect (unheated gems especially).
Experienced gemologists, observing the pleochroism of some gems, can successfully detect gemstones from other artificial stones using this instrument. Calcite dichroscope. There are two types of dichroscopes available: calcite and polarizing. Of the two, calcite gives better results and is widely used by experienced gemologists.
Rhodolite is a varietal name for rose-pink to red mineral pyrope, a species in the garnet group. It was first described from Cowee Valley, Macon County, North Carolina. [2] ...
Tanzanite was discovered in 1967 in Northern Tanzania. With its supply possibly declining in the next 30 years, this gemstone is considered to be more rare than a diamond. This type of gemstone receives its vibrant blue from being heated. [72] Hibonite was discovered in 1956 in Madagascar. It was named after the discoverer, French geologist ...
Dispersion: 0.017 [1]: Ultraviolet fluorescence: Pink stones; inert to very weak red to violet in long and short wave [1]: Absorption spectra: Strong narrow band at 498 nm, and almost complete absorption of red down to 640 nm in blue and green stones; red and pink stones show lines at 458 and 451 nm, as well as a broad band in the green spectrum [1]