Epidote Group – Zoisite and Epidote Composition
Zoisite
Composition. HCa2AL3si3O12 = Silica 39.7, alumina 33.7, lime 24.6, water 2.0.
Crystallization. Orthorhombic. Prismatic crystals usually without distinct terminations. Vertically striated.
Structure. In crystals; also massive.
Physical properties. H. = 6-6.5 G. = 3.25-3.37. vitreous luster. Color grayish white, green pink. Transparent to almost opaque.
Tests. Fuses at 3-4 with intumescences to a light colored slag. Yields a little water on intense ignition in C. T.
Occurrence. Usually in crystalline schists with one of the amphiboles. Thulite is a rose-pink variety.
Epidote
Composition. Ca2 (Al.OH) (Al,Fe)2 (SiO4)3. Iron occurs in varying amounts isomorphous with both the aluminum and calcium.
Crystallization. Monoclinic. Crystals are often much elongated parallel to the ortho-axis with a prominent development of the faces of the orthodome zone, giving them a prismatic aspect. Striated parallel to the ortho-axis. Terminated usually only at one end of the ortho-axis and most commonly by the two faces of a pyramid. Twinning shown at times.
Structure. Usually coarse to fine granular. In crystals. At times fibrous.
Physical Properties. Perfect basal cleavage. H. = 6-7. G. =3.23-3.45. vitreous luster. Color usually pistachio-green or yellowish to blackish green, sometimes gray. Transparent to opaque. Transparent varieties often show strong diachronic, appearing dark green in one direction, and brown in a direction at right angles to the first.
Test. Fuses at 3-4 with intumescences to a black slag. On intense ignition in C.T. yields a little water.
Occurrence. Epidote occurs commonly in the crystalline metamorphic rocks; as gneiss, amphibolites and various schists. Is formed frequently also during the metamorphism of an impure limestone. Is the product of alteration of such minerals as feldspar, pyroxene, amphibole, biotitic, scapolite, etc. Often associated with chorite. Notable localities for its occurrence in fine crystals are Knappenwand, Unterzulzbachthal, Salzburg, Austria; Bourg d´Oisans, Isére, France; the Ala Valley and Traversella, Piedmont; prince of Wales Island, Alaska; Haddam, Connecticut; Riverside, California.
Rod Mill Capacities Natrolite, Scolecite & Thomsonite Composition, Crystallization & Structure REFERENCES. Size of Feed to Crusher Modern Mine Prospectors Crushing Practices and Theories History of the Jaw Crusher Electromagnetic Methods GOLD MINING EQUIPMENT AUSTRALIA Fluorspar or fluorite (CaF2) a nonmetallic minerals and Flotation Refining Wireline Drilling Diamonds and the CSO Limonite - Brown Hematite, Bog-iron Ore Composition & Structure Mimetite Composition, Crystallization & Structure
