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Red, Gemmy Manganoneptunite

The Mineral manganoneptunite




Manganoneptunite is the manganese-dominant variant of Neptunite, having a greater portion of manganese over iron in a solid solution series. Although often considered a variety of Neptunite, the IMA recognizes Manganoneptunite as a distinct mineral species. Manganoneptunite is generally ligher in color than Neptunite, and can even be completely transparent in specimens where the iron content is very low.
Chemical Formula KNa2Li(Fe2+,Mn)2Ti2Si8O24
Composition Silicate of potassium, sodium, lithium, manganese, iron and titanium
Color Red, dark red, orange, brown, dark brown, black
Streak Dark brown
Hardness 5 - 6
Crystal System Monoclinic
Crystal Forms
and Aggregates		 As small tabular and prismatic crystals with a square cross-section. Also in complex crystals with many faces, and in tabular crystals with rhombic faces.
Transparency Transparent to nearly opaque
Specific Gravity 3.2 - 3.3
Luster Vitreous
Cleavage 1,1 - with 80 and 100 degree angles
Fracture Conchoidal
Tenacity Brittle
In Group Silicates; Nesosilicates
Striking Features Color and crystal habits, perfect cleavage, and locality/mode of occurrence.
Environment In nepheline syenite pegmatites.
Rock Type Igneous
Popularity (1-4) 3
Prevalence (1-3) 3
Demand (1-3) 3


Manganoneptunite AUCTIONS




NOTEWORTHY LOCALITIES
Manganoneptunite is not a common mineral, and is only found is a limited amount of deposits worldwide. The most notable locality for this mineral is Mont Saint-Hilaire, Québec, Canada, where small transparent, orange to dark-red crystals occur. Darker colored crystals are found nearby at the Demix-Varennes quarry, Varennes & St-Amable, Québec. Black lustrous Manganoneptunite crystals have been fround in the Aris Quarry, Windhoek District, Namibia; and black-cherry-red crystals from the Kola Peninsula in Russia.

COMMON MINERAL ASSOCIATIONS
Albite, Microcline, Aegirine

DISTINGUISHING SIMILAR MINERALS
Neptunite - Usually darker in color. Manganoneptunite also rarely forms in large crystals, as does Neptunite.


manganoneptunite PHOTOS
 
ADDITIONAL RESOURCES
 
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