Formula: (Ce,La,Nd,Th)PO4 Monoclinic Description: Monazite refers to a group of minerals dominated by various rare earth elements. These minerals commonly form reddish brown to yellowish tabular crystals and granular masses in granitic rocks and placer deposits derived …
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Molybdenite
Formula: MoS2 Hexagonal Description: Molybdenite is a relatively common hydrothermal mineral. It is most often found in vein complexes associated with granitic igneous rocks and related skarns that form at medium to high temperatures. It is economically …
Miserite
Formula: K(Ca,Ce)4Si5O13(OH)3 Triclinic Description: Miserite is a rare mineral that forms pinkish to lavender massive compact to scaly aggregates in complex granite pegmatites. MARATHON COUNTY: Brownish-pink to white prismatic crystals of miserite up to 1 cm across are …
Minnesotaite
Formula: (Fe,Mg)3Si4O10(OH)2 Triclinic Description: Minnesotaite is found frequently as small grains in iron formations that have experienced low grade metamorphism. It is often associated with stilpnomelane, cummingtonite, chlorite and siderite. Wisconsin localities for this minerals are restricted …
Minium
Formula: Pb3O4 Tetragonal Description: Minium is a rare mineral found as red dull to greasy masses in the oxidized zone of lead deposits where it forms as the result of the alteration of galena. IOWA COUNTY: Minium is …
Millerite
Formula: NiS Hexagonal Description: Millerite is a low temperature hydrothermal mineral found in vugs in carbonate rocks and as an alteration product of other nickel minerals. Millerite typically forms long brassy fibers making very aesthetic specimens. …
Microlite
Formula: (Na,Ca)2Ta2O6(O,OH,F) Isometric Description: Microlite refers to a group of rare minerals related to pyrochlore that form equant to irregular pale yellow, brown, red or green grains in complex granite pegmatites. FLORENCE COUNTY: Microlite occurs with lepidolite …
Meteorites
Formula: Varies Description: Mifflin L5 chondrite meteorite fragment showing internal brecciation. (Image courtesy John Valley; unauthorized reproduction is prohibited.) CLARK COUNTY: Two stony meteorites with a combined weight of over 200 pounds fell at 6:15 P.M. on …
Metavivianite
Formula: Fe3(PO4)2(OH)2.6H2O Triclinic Description: Metavivianite is a rare phosphate mineral formed by the alteration of vivianite and other phosphate minerals. RUSK COUNTY: Forms dark to pale green crystals and coating on vivianite from the oxidized zone, Flambeau …
Metavariscite
Formula: AlPO4.2H2O Monoclinic Description: Metavariscite is a pale-green mineral found as granular masses or small tabular crystals precipitated by ground water in association with other phosphate minerals. DODGE COUNTY: Metavariscite is a microscopic component of the oolites …