Staurolite Composition, Crystallization & Structure

Composition. A ferrous iron-aluminun silicate, Hal5 Fe Si2O13.

Crystallization. Orthorhombic. Habit prismatic, showing usually a combination of pris with large angle (130°), brachypinacoid, base and macrodome. Cruciform twins very common; of two types, (1) in which the two individuals cross at nearly 90°, (2) in which they cross at nearly 60°. Sometimes both types are combined in one crystal.

Structure. Usually in crystals.

Physical Properties. H. = 7-7.5. G. = 3.65-3.75. Resinous to vitreous luster, for pure and fresh material; often dull to earthy when altered or impure. Color red-brown to brownish black. Translucent to opaque.

Test. Infusible. Insoluble. On intense ignition in C. T. Yields a little water. Often very impure. Recognized by its characteristic crystals and twins.

Occurrence. Staurolite is an accessory mineral in metamorphic rocks; in crystalline schists, slates, and sometimes in gneisses. Often associated with garnet, cyanide, silmanite, tourmaline. Notable localities for its occurrence are Monte Championed, Switzerland; in Brittany; Windham, Maine; Franconia and Lisbon, New Hampshire; Chesterfield, Massachusetts; fanny County, Georgia.

Name. Derived from a Greek word meaning cross, in allusion to its cruciform twins.

Use. Occasionally a transparent stone from Brazil is cut as a gem.

Geological Sampling. How to collect a representative sample for testing Metallurgy and Assays. General Geology Nitrogen & Copper-Nickel Ore Conditioning for Flotation Curves Show % of Critical Speed of Mill Solubility Theory and minerals Floatability - sulfide minerals extreme in the requirement for surge capacity Curves Show % of Critical Speed Table - Chart to Sizing a Shovel Dipper Jadeite and Wollastite Composition, Crystallization & Structure Haulage of Ore Proustite - Light Ruby Silver Composition, Crystallization and Structure REFERENCES. Crushing Plant Noise Antimony Elements, Alloys and Symbols