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.

Chemical Formula

Na₈Al₆Si₆O₂₄(SO₄) · H₂O

Color

Bright blue, light blue, grayish-blue, gray, black, white, yellow, brown, colorless

Crystal System

Isometric

Properties

Streak Light blue to white

Hardness 5.5

Transparency Transparent to translucent

Specific Gravity 2.3 - 2.4

Luster Vitreous, waxy

Cleavage 1,2

Fracture Uneven

Tenacity Brittle

Crystal Habits

As coatings on interconnected dodecahedral crystals, in octahedral crystals, as complex prismatic microcrystals, grainy, and massive.

Additional Information

Composition Hydrous sodium calcium aluminum silicate with sulfate

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

Other Names

Noselite

Noteworthy Localities

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.

Common Mineral Associations

Nepheline, Sodalite, Phlogopite, Calcite, Scapolite, Sanidine

nosean Photos

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