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 […]
MAUCHERITE
MAUCHERITE Maucherite – Ni11As8 – is a very rare arsenide found in Co-Ni-As-Ag sulfide ores. It may contain Co, Fe, Sb, Cu, and S. 1. Characteristics Crystal system: Tetragonal trapezohedral. Color: Reddish silvery-white, tarnishing to a darker reddish-gray (like copper). Habit: Tabular // a (001). Also pyramidal; crystals up to 1 mm.Massive, granular, rarely radially […]
MELILITE
MELILITE Melilite – (Ca,Na)2(Mg,Al)(Si,Al)2O7 – is a rarer sorosilicate, typical of alkaline volcanic rocks. It has no economic importance. “Melilite” is not a mineral, but merely a generic term referring to minerals of the Melilite Group, a solid solution composed of nine members: akermanite, alumoakermanite, bennesherite, ferri-gehlenite, gehlenite, gugiaite, hardystonite, hydroxygugiaite, and okayamalite. The most […]
MEIONITE
MEIONITE See “Scapolite”
MARIALITE
MARIALITE See “Scapolite”
MONAZITE
MONAZITE Monazite – (Ce,La,Th,Sm)PO4 – is a common phosphate. It was an important ore of Th, La and Ce, before the world market for Rare Earth Elements was dominated by the Mongolian occurrences exploited by China. It still remains as REE ore, but on a very small scale. “Monazite” nowadays no longer designates a mineral […]