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 […]
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, […]