Fluornatrocoulsellite is a rare member of the eudialyte group found in alkaline igneous complexes. Collectors identify it by its specific trigonal habit and its association with other rare alkaline minerals, though it is often indistinguishable from eudialyte without chemical analysis.
Is this fluornatrocoulsellite?
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 fluornatrocoulsellite with a known reference. Fluornatrocoulsellite sits at Mohs 4.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: colorless, white.
- 5Look at form & habitCrystal system: trigonal. Typical habit: equant crystals, granular aggregates.
Often confused with
Fluornatrocoulsellite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside fluornatrocoulsellite
Minerals reported to co-occur with fluornatrocoulsellite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Na₁.₅Ca₀.₅)(Mg₁.₅Al₀.₅)F₆F
- Mohs hardness
- 4.5
- Density
- 2.99 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent to translucent
- Crystal system
- Trigonal
- Crystal habit
- Equant crystals, granular aggregates
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector, Scientific research
- Host rock
- In replacement lenses formed during greisenization
Where rockhounds find fluornatrocoulsellite
Classic worldwide localities
- Cleveland tin mine, 14 km southwest of Waratah, Luina township, western Tasmania, Australia
Field-hunting tip
Where it forms: In replacement lenses formed during greisenization. If you start seeing morinite, gearksutite, vivianite in float, you are in the right ground. Typical habit: equant crystals, granular aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify fluornatrocoulsellite?+
Where is fluornatrocoulsellite found?+
What rocks look like fluornatrocoulsellite?+
What minerals are found with fluornatrocoulsellite?+
What kind of rock does fluornatrocoulsellite form in?+
What is fluornatrocoulsellite used for?+
Find fluornatrocoulsellite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
