Nosean is a member of the sodalite group often found in undersaturated volcanic rocks like phonolites and tephrites. It typically occurs as dodecahedral crystals and is highly prized by collectors for its strong orange fluorescence under ultraviolet light.
Is this nosean?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch nosean with a known reference. Nosean sits at Mohs 5.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: bluish white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: gray, white, blue, green, brown.
- 5Look at form & habitCrystal system: cubic. Typical habit: massive.
Often confused with
Nosean vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Nosean leaves bluish white, Sodalite leaves white.
How to tell apart: Streak differs, so Nosean leaves bluish white, Haüyne leaves slightly bluish to colorless.
How to tell apart: Streak differs, so Nosean leaves bluish white, Lazurite leaves bright blue.
Often found alongside nosean
Minerals reported to co-occur with nosean. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Na₈(Si₆Al₆)O₂₄(SO₄)·H₂O
- Mohs hardness
- 5.5
- Density
- 2.30-2.40 g/cm³
- Streak
- Bluish white
- Luster
- Vitreous
- Transparency
- Transparent to translucent
- Crystal system
- Cubic
- Crystal habit
- Massive
- Cleavage
- {110}, indistinct
- Rarity
- Uncommon
- Uses
- Collector, Scientific research
- Host rock
- In silica-deficient alkalic volcanic rocks, principally phonolites
Where rockhounds find nosean
Classic worldwide localities
- Black Hills, Lawrence Co., South Dakota, and in the Cripple Creek district, Teller Co., Colorado, USA
- Schellkopf, near Brenk, around the Laacher See, Eifel district, Germany
- Dutchlingen and in the Höwenegg quarry, Hegau, Baden-Württemberg, Germany
- Mont-Dore massif, Auvergne, and at Vinsac, Aldis, and Cournil, Cantal, France
- Wolf Rock, Cornwall, England
- Covao, Cape Verde Islands
Field-hunting tip
Where it forms: In silica-deficient alkalic volcanic rocks, principally phonolites. If you start seeing sanidine, mica, leucite in float, you are in the right ground. Typical habit: massive. Train your eye for that shape before scanning the outcrop.
Common questions
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Find nosean on the map
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