name = Almandine
color = reddish orange to red, slightly purplish red to reddish purple and usually dark in tone
cleavage = none
fracture = conchoidal
mohs = 7 - 7.5
luster = greasy to vitreous
polish = vitreous to subadamantine
refractive = 1.790 (+/- .030)
Gemological Institute of America, "GIA Gem Reference Guide" 1995, ]
opticalprop = Single refractive, and often anomalous double refractive
birefringence = none
dispersion = .024
pleochroism = none
absorption = usually at 504, 520, and 573nm, may also have faint lines at 423, 460, 610 and 680-690nm
gravity = 4.05 (+.25, -.12)
Almandine, also known incorrectly as almandite, is a species of mineral belonging to the
garnetGroup. The name is a corruption of alabandicus, which is the name applied by Pliny the Elderto a stone found or worked at Alabanda, a town in Caria in Asia Minor. Almandine is an iron alumina garnet, of deep red color, inclining to purple. It is frequently cut with a convex face, or en cabochon, and is then known as carbuncle. Viewed through the spectroscope in a strong light, it generally shows three characteristic absorption bands. Almandine is one end-member of a mineral solid solutionseries, with the other end member being the garnet pyrope. The almandine crystal formula is: Fe3Al2(SiO4)3. Magnesiumsubstitutes for the ironwith increasingly pyrope-rich composition.
Almandine occurs rather abundantly in the gem-gravels of
Sri Lanka, whence it has sometimes been called Ceylon-ruby. When the color inclines to a violet tint, the stone is often called Syrian garnet, a name said to be taken from Syriam, an ancient town of Pegu. Large deposits of fine almandine-garnets were found, some years ago, in the Northern Territory of Australia, and were at first taken for rubies and thus they were known in trade for some time afterwards as Australian rubies.
Almandine is widely distributed. Fine rhombic
dodecahedraoccur in the schistose rocks of the Zillertal, in Tyrol, and are sometimes cut and polished. An almandine in which the ferrous oxide is replaced partly by magnesia is found at Luisenfeld in German East Africa. In the United Statesthere are many localities which yield almandine. Fine crystals of almandine embedded in mica-schist occur near Fort Wrangell in Alaska. The coarse varieties of almandine are often crushed for use as an abrasiveagent.
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