Epidotes (silicates): Allanite
Diagnostic card.
(Ca, Ce) 2 (Fe 2+ , Fe 3+ ) Al 2 O OH SiO 4 Si 2 O 7
Singonia monoclinic
Hardness 5-6
Specific weight 3,9-4
Cleavage imperfect
Cracked shell
Color from brown to black
Color in powder greenish-gray, brown
Shine from the floor of metal to resin
Crystallizes in the monoclinic system. Forms short-columnar or elongated crystals, as well as lamellar by basal pinacoid. It is often found in the form of irregular grains or bean-shaped aggregates, as well as dense massive clusters.
Diagnostic signs.
It dissolves in nitric acid, giving an amorphous silica residue. When heated, it increases in volume, fusing into a greyish-black magnetic mass.
Origin.
This is a fairly common accessory mineral of igneous rocks, such as granites, syenites and diorites. It also occurs in crystalline schists and gneisses.
Place of Birth.
The most famous locations are Miass in the Urals, Falun, Itterby and Sheppsholm in Sweden. Allanite is also found in Greenland, Madagascar, Norway and the United States. Dark gray short-columned crystals are noted in the granites of Baveno and others near Adamello.
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