GLAUCONITE
GLAUCONITE Glauconite – (K,Na)(Mg,Fe+2,Fe+3)(Fe+3,Al)(Si,Al)4O10(OH)2 – is a common phyllosilicate in marine sediments and sedimentary rocks. It has no economic importance. For decades it was believed that glauconite and celadonite were the same mineral. Therefore, care must be taken with old samples, which may have the wrong designation. Celadonite may contain Ti, Ca, and P as […]
GRAPHITE
GRAPHITE Graphite – C – a native element, is easy to recognize macroscopically due to its bright gray color, lamellar shape, unctuous feel and being very soft, it get your fingers dirty. It is very similar to molybdenite (MoS2), which it was confused with for a long time. It is not a common mineral; in […]
GRUNERITE
GRUNERITE Grunerite – ☐{Fe22+}{Fe52+}(Si8O22)(OH)2 – is an inosilicate from the Amphibole Group. It is a rarer mineral, with some very specific parageneses. It was mined as “asbestos” in its fibrous form – “amosite” – but the worldwide trend is to end the mining and use of the various minerals considered as “asbestos”. It is classified […]
GOLD
GOLD Gold – Au – is a native element that constitutes ore of gold and other elements. Aesthetic pieces fetch prices much higher than the standard price of gold in the collector minerals market. Gold always forms mixing crystals. It forms a series with silver and usually contains Ag, Cu and Fe, more rarely I, […]
GOETHITE
GOETHITE Goethite – FeO(OH) – is a very common oxide, abundant in various types of rocks and in soils. It participates in the composition of many Fe and Mn ores. Goethite can form prismatic crystals, striated parallel to [001], up to 45 cm long. Tabular crystals according to {010} also occur. However, the most common […]
GARNET
GARNET Garnet – A3B2(SiO4)3 A=(Mg,Mn,Ca,Fe), B=(Al,Cr,Fe) – is a very common nesosilicate, which can be found in igneous, metamorphic and sedimentary rocks. It is an important industrial mineral with many applications, mainly as an abrasive. “Garnet” is actually not a mineral, but just a generic term referring to members of the Garnet Group: pyrope – Mg3Al2(SiO4)3, […]
GLAUCOPHANE
GLAUCOPHANE Glaucophane – Na2(Mg, Fe)3Al2Si8O22 (OH)2 – is an inosilicate of the Amphibole Supergroup, typical of high pressure and low temperature metamorphic rocks of the blueschist facies. It has no economic importance. Glaucophane forms a series with riebeckite. “Crossite” is a term now discredited that designated minerals with intermediate compositions between glaucophane and riebeckite. […]
GALENA
GALENA Galena – PbS – is a very common sulphide, the main ore of Pb and often an important ore of Ag. Pb-Zn ores generally contain economic grades of Cu, Ag, Sb and Bi. Galena always contains varying, usually very low, levels of Ag, Cu, Fe, Tl, Mn, Zn, Cd, Sb, As and Bi. Many […]