Linnaeite Composition, Crystallization and Structure
A sulphide of cobalt, Co3S4 or coS. Co2S3 with the cobalt replaced in varying amount by nickel. Isometric. In small octahedral crystasl or granular massive. H. = 5.5. G. = 4.9. Metallic luster. Color pale steel-gray. Grayish black streak. Fusible at 2. Gives odor of sulfur dioxide in O. T. Fuses in R. F. to a magnetic globule. Roaster mineral colors the borax bead blue (cobalt). A rare mineral, found with chalcopyrite near Riddarhyttan, Sweden; with barite and siderite at Musen, Prussia; with lead ores at Mine La Motte, Missouri.
Chalcopyrite.- Copper Pyrites. Yellow Copper Ore
Composition: A sulphide of copper and iron, CuFeS2 = Sulfur 35, copper 34.5, iron 30.5.
Crystallization: tetragonal; sphenoidal. Crystals usually in unit sphenoids , which because the vertical axis is close to unity (c = 0.985) are very near to the isometric tetrahedron in angles. Steeper spheroid’s, and other more complex forms occasionally observed.
Structure. Usually massive, compact; at times in crystals.
Physical Properties. H. = 3.5. G. = 4.2-3.3. Metallic luster. Color brass-yellow; often tarnished to bronze or iridescent. Streak greenish black.
Tests. Easily fusible to a ,macnetic globule. Gives odor of sulfur dioxide when heated B. B. or in O. T. Gives sulfur in C. T. After roasting, and moistening with hydrochloric acid, gives an azure-blue flame. Readily decomposed by nitric acid, giving separated sulfur; solution made ammoniacal gives red brown precipitate of ferric hydroxide and blue filtrate (copper). Recognized by its brass-yellow color, greenish lack streak and its softnes. Distinguished from pyrite by its being softer than steel and fro gold by its being britle. Known sometimes as “fool’s gold,” a term which is also applied at times to pyrite.
Occurrence. The most common ore of copper. Occurs widely distributed in metallic veins associated with pyrite, pyrrhotite, bornite, chalcocite, tetrahedrite, malachite , azurite, shalerite, galena quartz, calcite, dolomite, siderite, etc. It is commonly of primary origin and from it, by various alteration processes, many other copper minerals are derived. Also occurs as an original constituent of igneous rocks; in pegmatite veins; in contact metamorphic deposits: disseminated in schistose rocks; etc . May carry gold or silver and become an ore of hose metals. Often on subordinate amount with large bodies of pyrite, making them serve as low-grade copper ores. Chiefly ore of copper mines at Cornawall, England; Falun, Sweden; Rio Tinto, Spain; Sudbury, Canada; in South Africa, Chile, etc. Found widely in the United States but usually in connection with other copper minerals in equal or greater amount; found at Butte, Montana; Bingham, Utah; various districts in California, Colorado; Arizona, etc.
Name. Derived from Geek word meaning brass and from pyrites.
Use. Most important ore of copper.
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