ARFVEDSONITE
ARFVEDSONITE Arfvedsonite – [Na] [Na2] [Fe2+4Fe3+] Si8O22(OH)2 – is an inosilicate, a sodium amphibole, quite rare, typical of rare alkaline rocks. It has no economic use; it is found on the market only as a mineral for collectors. “Arfvedsonite” is not actually a mineral, but just a generic term used to designate the Arfvedsonite Group’s […]
ARAGONITE
ARAGONITE Aragonite – CaCO3 – is a fairly common carbonate, but much rarer than calcite, the most common polymorph of Ca carbonate; the third is vaterite (very rare). It does not constitute ore, but aesthetic pieces fetch a competitive price in the collector minerals market. It is the main member of the Aragonite Group. May […]
AZURITE
AZURITE Azurite – Cu3(CO3)2(OH)2 – is a carbonate of copper and has a deep blue color that is unmistakable, extremely characteristic. Integrates oxidized copper ores. In addition, well-formed crystals of azurite fetch very high prices in the collector minerals market. It forms prismatic crystals that are translucent at the sharp edges. The crystals reach up […]
AUGITE
AUGITE Augite – (Ca,Na)(Mg,Fe,Al,Ti)Si2O6 – is an inosilicate of the Pyroxene Supergroup. It is a very common clinopyroxene (monoclinic pyroxene), an important rock forming mineral of basic igneous rocks (basalts, etc.), but it has no economic importance. It is part of a solid solution formed by diopside (CaMgSi2O6), augite and hedenbergite (CaFe2+Si2O6). There are four […]
ACTINOLITE
ACTINOLITE Actinolite – Ca2(Mg,Fe)5Si8O22(OH)2 – is an inosilicate of the Amphibole Supergroup. It is a very common mineral, typical of metamorphic rocks. It is mined when it occurs with fibrous habit and is marketed as “asbestos”, but this usage is less and less due to health concerns. The variety “nephrite” is one of the two […]
ANATASE
ANATASE Anatase – TiO2 – is a relatively common oxide. It occurs as an accessory mineral in many igneous and metamorphic rocks and easily goes unnoticed. It does not constitute an ore. Anatase is one of the five polymorphs of titanium oxide found in nature. The most common are brookite and rutile. Anatase may contain […]
ANDESINE
ANDESINE See “PLAGIOCLASE”
ANORTITE
ANORTITE See “PLAGIOCLASE”
ALBITE
ALBITE Introduction See “PLAGIOCLASE”
AMBER
AMBER Amber is a low-density amorphous fossil plant resin, used since the Neolithic times as a gemstone and still reaching very high prices due to the huge demand created by the Chinese market. The color of amber varies from very light yellow to honey and black. There is amber from the Dominican Republic that is […]