ARSENOPYRITE
ARSENOPYRITE Arsenopyrite – FeAsS – is a very common sulfide and constitutes an ore of As, but As is usually recovered as a by-product processing ores of other elements. Arsenopyrite has a high content (46%) in As and a turbulent history of exploration, with over 40 names currently discredited. May contain high levels of Au. […]
ALGODONITE
ALGODONITE Algodonite is a rare arsenide that integrates complex ores of Cu and Ag with As.It may contain Ag, and there is a synthetic variety with Ag.In older literature, there is a differentiation between α-algodonite and β-algodonite. Similarly, domeykite, which occurs in association, was “subdivided” into α-domeykite, β-domeykite, and γ-domeykite. Some references even mention δ-forms, […]
APOPHYLLITE
APOPHYLLITE Apophyllite is a relatively common phyllosilicate, typically a secondary mineral associated with basic igneous rocks. It does not constitute ore, but it has acceptance among collectors. For decades there has been collection and commercialization of pieces with apophyllite in India, in the basaltic rocks of the “Traps” of the Deccan. In reality, “apophyllite” is […]
APATITE
APATITE “Apatite” – (Ca5(PO4))3(F,OH,Cl) – is not a mineral, but a term used for members of a group of isomorphic minerals formed by apatite-(CaF) (very common), apatite-(CaOH) (much less common, forms teeth and bones) and apatite -(CaCl) (very rare). In hand samples they are practically indistinguishable and each one can partially replace the others. These […]
ANTHOPHYLLITE
ANTHOPHYLLITE Anthophyllite – ☐{Mg2}{Mg5}(Si8O22)(OH) – is an inosilicate of the Amphibole Supergroup. It is a rarer amphibole, typical of medium to high grade metamorphic rocks. Anthophyllite with a fibrous habit is one of the six minerals known as “asbestos” and was mined in some locations until the 1970s, when mines were closed due to problems […]
ANHYDRITE
ANHYDRITE Anhydrite – CaSO4 – is a very common anhydrous sulfate, an important constituent of evaporitic sequences and related deposits. It is a very important ore. Anhydrite is usually very pure, but may contain Sr and Ba. It has fusibility 2 (melts in the candle flame). Anhydrite crystals reach 15 cm in length, with 40 […]
ANDALUSITE
ANDALUSITE Andalusite – Al2SiO5 – is a relatively common nesosilicate, characteristic of some types of metamorphic rocks. It could be used as a raw material for silico-aluminous refractories, but seldom occurs in economically viable volumes. It is one of the polymorphs of the Al2SiO5 Group: kyanite, sillimanite and andalusite. Forms a series with kanonaite (Mn3+Al(SiO4)O). […]
ANALCIME
ANALCIME Analcime – Na2(Al2Si4O12).2H2O – is a tectosilicate from the Zeolite Group. It is a relatively rare mineral, commonly found in association with other zeolites. It has no economic importance others than the market for mineral collectors. The chemistry and structure of analcime are more similar to those of feldspathoids. It is cubic/pseudocubic, but can […]
ALUNITE
ALUNITE Alunite – KAl3(SO4)2(OH)6 – is a relatively common sulfate, mined as a source of alum (KAl(SO4)2-12H2O), as an ore of Al (36.92% Al2O3) and K (11.37% K2O) or as a raw material for potassium fertilizers. It is a traditional and important ore in certain regions, as alunite occurrences are very common; some deposits are […]
ALLANITE
ALLANITE Allanites – (Ca,Mn,Ce,Y,Th,La)2(Fe,Ti,Al)3O(Si2O7)(SiO4)(OH) – are relatively common sorosilicates that constitute ore of Rare Earth Elements (REEs), as they can contain up to 20% of them. In reality, “allanite” does not designate a mineral, but is just a generic name for the minerals that make up the Allanite Group, classified in the Epidote Supergroup. Based […]