MONTICELLITE
MONTICELLITE Monticellite – CaMgSiO4 – is a rare nesosilicate that occurs mainly in magnesian skarns. It has no importance as an ore. It is classified in the Olivine Group and may contain Al, Fe, Ti, Zn, Mn, and H2O as impurities. Forms a series with kirschsteinite. 1. Characteristics Crystal system: Orthorhombic pipyramidal. […]
MONTEBRASITE
MONTEBRASITE Montebrasite – LiAl(PO4)(OH) – is a relatively rare phosphate, typical of granitic pegmatites. It has been used as a Li ore and is sometimes cut as a gemstone. It is classified in the Amblygonite Group, in the Amblygonite-Montebrasite Series. Montebrasite may contain Na. It sometimes exhibits fluorescence in orange colors under long-wave ultraviolet light. […]
MACKINAWITE
MACKINAWITE Mackinawite – (Fe,Ni)9S8 – is a relatively common sulfide, also described as (Fe,Ni)1+xS (x = 0 – 0.11). It is part of polymetallic ores of Cu, Ni, and Co as a product of unmixing or alteration. It is much more common than valleriite, with which it was confused for decades. Under a microscope, it […]
MIMETITE
MIMETITE Mimetite – Pb5(AsO4)3Cl – is a rarer arsenate, typically a secondary mineral in Pb deposits. It is part of oxidized Pb ores, but is never the main ore mineral in the deposit. Aesthetic pieces fetch high prices in the collector mineral market. It is classified in the Apatite Group, a group of isomorphic hexagonal […]
MIARGYRITE
MIARGYRITE Miargyrite – AgSbS2 – is a relatively rare sulfide that occurs in subordinate quantities in low-temperature epithermal hydrothermal veins with Ag sulfides. It is an Ag ore. Miargyrite is the monoclinic trimorph of cuboargyrite (isometric AgSbS2) and baumstarkite (Ag3Sb3S6 , triclinic). It may contain As and Fe as impurities. 1. Characteristics Crystal system: Monoclinic […]
MAGNESITE
MAGNESITE Magnesite – MgCO3 – is a relatively common anhydrous carbonate, which constitutes an important industrial mineral when it occurs in large volumes and with high purity, used in the manufacture of refractories. Magnesite forms a series with gaspeite (carbonate of Ni, Mg, and Fe), another series with siderite (carbonate of Fe), and an incomplete […]
MICROLITE
MICROLITE Microlites – (Na,Ca)2Ta2O6(O,OH,F) or A2-mTa2X6-wZ-n – constitute a group of relatively rare oxides that are ore of Ta. The Microlite Group is formed by the Ta-rich (and Ti- and Nb-poor) members of the Pyrochlore Supergroup. There are 13 different mineral species, plus 6 varieties. They are minerals that generally occur in the form of […]
MOLYBDENITE
MOLYBDENITE Molybdenite – MoS2 – is the most abundant molybdenum mineral and the main molybdenum ore mineral. It is the only rhenium ore, as it always contains Re in levels from ppm to 1-2%. Jordisite is still amorphous MoS2, found in semi-metallic masses in some deposits. Wulfenite – Pb(MoO4) – is formed from jordisite. Jordisite alters […]
MORDENITE
MORDENITE Mordenite – (Na2, Ca,K2)Al2Si10O24.7H2O – is a tectosilicate from the Zeolite Group. It is relatively common, more easily observed when it occurs in cavities (vesicles of volcanic rocks). It has no importance as an ore. The largest crystals reached 2.5 cm. May contain Mg. 1. Characteristics Crystal system: Orthorhombic piramidal. […]
MARCASITE
MARCASITE Marcasite – FeS2 – is a common sulfide found in a variety of paragenetic settings. It is not an ore mineral. In gemology, the term “marcasite” historically refers to pieces actually crafted from pyrite; marcasite itself cannot be faceted due to its tendency to break and alter easily. Marcasite (orthorhombic) is dimorphous with pyrite […]