COPPER
COPPER Copper – Cu – is a relatively common native element, which was locally a very important copper ore, as in Keeweenaw (Michigan, USA). Aggregates with crystalline forms reach prices in the market of collect minerals much higher than the price of the contained metal. Copper typically forms dendritic aggregates, lamellae, plates, vanes, wires and […]
CLINOZOISITE
CLINOZOISITE Clinozoisite – Ca2Al3O(SiO4)(Si2O7)(OH) – is a sorosilicate from the Epidote Group. It is a somewhat less common mineral, characteristic of some types of metamorphic rocks. It has no economic importance. Clinozoisite, in the Epidote Group with epidote and piemontite, is dimorphic with zoisite, forms a series with epidote, and may contain Mn, Mg, Ti, […]
COSALITE
COSALITE Cosalite – Pb2Bi2S5 – is a fairly rare sulfosalt, typical of hydrothermal veins of the Pb-Bi-Cu-Ag association. It is part of polymetallic ores, but is never the main ore mineral of the deposit. It always has some Cu and almost always contains some Ag; both seem to be essential, resulting in a formula CuxAgi-sPb8-2s-0,5(x+i)Bi8+sS20 […]
COVELLITE
COVELLITE Covellite – CuS – also known as “covelline”, is a very common sulfide, an ore of Cu. It may be the main Cu ore mineral in the deposit, but is usually of minor importance, occurring in small amounts as alteration material. Macroscopically it can be recognized by its deep blue, almost black color. However, […]
CASSITERITE
CASSITERITE Cassiterite – SnO2 – is a relatively rare oxide that constitutes the main ore of Sn. It is classified in the Rutile Group and may contain Fe, Nb, Ta, Zn, W, Mn, Sc, Ge, In and Ga. It rarely forms botryoidal masses, called “wood tin”, which is one of the four varieties recognized for […]
CHLORITE
CHLORITE Chlorite – (Mg,Al,Fe)3(Si,Al)4O10(OH)2.(Mg,Al,Fe)3(OH)6 – is a very common phyllosilicate that can occur in many types of igneous, metamorphic and sedimentary rocks. It has no economic importance. “Chlorite” is actually not a mineral, but just a generic term applied to the phyllosilicates that make up the 12-member Chlorite Group. The most common are clinochlore (of […]
CHROMITE
CHROMITE Chromite – FeCr2O4 – is a relatively common oxide and constitutes the most important ore of chromium. The name “chromite” is commonly used to designate any Cr-rich mineral of the Spinel Group, especially for the chromite-magnesiochromite series. As pure chromite is extremely rare, the “chromites” in the literature are actually magnesiochromites, which is another […]
CLAY MINERALS
CLAY MINERALS Clay minerals are phyllosilicates that occur in very small sizes (“clay size”, corresponding to sizes less than 2 microns) and therefore cannot be identified under the petrographic microscope. The most usual analytical technique for its identification is X-Ray Diffractometry, which submits the samples to 3 analyzes (natural, glycolated and calcinated). The results, analyzed […]
CHALCOCITE
CHALCOCITE Chalcocite – Cu2S – is a relatively common sulfide, being one of the most profitable Cu ores, with almost 80% by weight Cu. Crystals are very rare and obtain high prices in the market of collectible minerals. The planetary abundance of copper and sulfur, its wide distribution in the most varied geological environments and […]
CUMMINGTONITE
CUMMINGTONITE Cummingtonite – (Mg,Fe2+)2(Mg,Fe2+)5Si8O22(OH)2 – is an inosilicate of the Amphibole Supergroup. It is a very rare mineral, characteristic of some types of metamorphic rocks. It does not currently constitute ore. A very rare fibrous variety, “amosite” (AMOSA = Asbestos Mine of South Africa) was mined as “asbestos” in South Africa. It is defined as […]