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Rare Black Nosean Octahredron

The Mineral nosean

Nosean is an uncommon member of the feldspathoid group that is closely related to Lazurite and Hauyne. It can sometimes be very difficult to distinguish these three minerals without a complex chemical analysis. Nosean forms a solid solution series with Hauyne, where Hauyne contains calcium in place of some of the sodium, whereas Nosean lacks any calcium and has water in its chemical structure.

Nosean is named after German mineralogist and chemist Karl Wilhelm Nose (1753-1835).
Chemical Formula Na8Al6Si6O24(SO4) · H2O
Composition Hydrous sodium calcium aluminum silicate with sulfate
Color Bright blue, light blue, grayish-blue, gray, black, white, yellow, brown, colorless
Streak Light blue to white
Hardness 5.5
Crystal System Isometric
Crystal Forms
and Aggregates
As coatings on interconnected dodecahedral crystals, in octahedral crystals, as complex prismatic microcrystals, grainy, and massive.
Transparency Transparent to translucent
Specific Gravity 2.3 - 2.4
Luster Vitreous, waxy
Cleavage 1,2
Fracture Uneven
Tenacity Brittle
In Group Silicates; Tectosilicates; Feldspathoid Group
Striking Features Color and mode of occurrence
Environment In alkali-rich, altered volcanic environments, nepehline syenites, and marbles.
Rock Type Igneous, Metamorphic
Popularity (1-4) 3
Prevalence (1-3) 3
Demand (1-3) 2


Exceptional Nosean with an electric-blue color comes from Sar-e Sang, Kokcha Valley, Badakshan Province, Afghanistan, where it forms most often as a significant inclusion of Sodalite coating Nepheline. Complex, prismatic colorless microcrystals of Nosean come from the In den Dellen quarries, Niedermendig, Eifel Mountains, Germany; and well-formed microcrystals from Vetralla, Vico Lake, Viterbo Province, Latium, Italy.

Nepheline, Sodalite, Phlogopite, Calcite, Scapolite, Sanidine

nosean PHOTOS
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