POWELLITE
POWELLITE Powellite – Ca(MoO4) – is a rare molybdate that forms as a secondary mineral. It rarely forms an ore, despite molybdenum being a strategic element. Powellite crystals, on the other hand, fetch high prices in the collector mineral market. Powellite is classified in the Scheelite Group and forms a solid solution series (it is […]
PSEUDOBROOKITE
PSEUDOBROOKITE Pseudobrookite – Fe2TiO5 – is a rare oxide, typical of Ti-rich igneous rocks. It has no importance as an ore. It is classified in the Armalcolite-Pseudobrookite Series, and there is a polymorph of it, still unnamed. There are many synthetic analogues. It can form epitaxies with hematite and magnetite. It may contain rutile inclusions. […]
PETALITE
PETALITE Petalite – LiAl(Si4O10) – is a fairly rare phyllosilicate, a lithium ore. In this case, it is “hard rock lithium ore”, which are lithium ores from pegmatites. The other type of lithium ore is “brines,” which are brines mined in salt flats, such as those in the Andes, for example. Petalite forms crystals up […]
PARGASITE
PARGASITE Pargasite – NaCa2(Mg4Al)(Si6Al2)O22(OH)2 – is an inosilicate, an amphibole, with a very restricted occurrence. It has no economic importance beyond its occasional use as a gemstone. Petrologically, it is important because it constitutes the main reservoir of water in the upper mantle. It is classified in the Amphibole Supergroup, where it gives its name […]
PERICLASE
PERICLASE Periclase – MgO – is a rare oxide, typical of some dolomitic marbles. It is not an ore. Periclase generally has a stoichiometric composition, but up to 10% Fe can replace Mg. When high in Fe, it constitutes the ferro-periclase variety which, when altered, forms brucite and iron oxides separately. Some sources consider the […]
PLATTNERITE
PLATTNERITE Plattnerite – PbO2 – is an extremely rare oxide, typically a secondary Pb mineral. It is part of oxidized Pb-Zn-Cu ores, but has no economic importance. It is classified in the Rutile Group. It is composed of β-PbO2 and is dimorphic with scrutinyite (α-PbO2), which is also extremely rare. 1. Characteristics Crystal system: Tetragonal, […]
PROUSTITE
PROUSTITE Proustite – Ag3AsS3 – is a fairly rare sulfosalt, an important Ag ore. In deposits, its volume varies greatly, and in only some cases is it the main Ag ore. It is called “ruby silver ore” because of its red internal reflections. The mining term “ruby silvers” is used interchangeably for proustite, pyrargyrite, miargyrite, […]
PEROVSKITE
PEROVSKITE Perovskite – CaTiO3 – is a rarer oxide; it usually occurs as an accessory mineral in some types of plutonic rocks. It has economic interest due to its content of Rare Earth Elements such as Ce, La, Nd, and others. These REEs have given rise to several special names for perovskite, such as knopite, […]
PLATINUM (Native)
PLATINUM (Native) Native platinum is an extremely rare native element that, in addition to platinum ore, is a source of Os, Ir, and other rare elements.Platinum – Pt – is one of the rarest elements in the Earth’s crust. Native platinum is consequently very rare, usually found as rolled grains, in nuggets. The largest masses […]
PLAGIONITE
PLAGIONITE Plagionite – Pb5Sb8S17 – is a very rare sulfosalt that occurs in hydrothermal vein deposits, especially in Pb-Zn veins. It is part of Pb-Sb-Ag-Zn ores. It is classified in the Plagionite Group and may contain Ag as an impurity. 1. Characteristics Crystal system: Monoclinic prismatic. Color: Dark lead gray (“blackish”) […]