Sellaite is a relatively rare magnesium fluoride mineral that typically forms as small, clear, prismatic crystals. It is most often discovered in hydrothermal veins and sedimentary evaporite environments, often associated with other fluoride-bearing minerals like fluorite.
Is this sellaite?
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 sellaite with a known reference. Sellaite sits at Mohs 5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Sellaite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Sellaite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: colorless, white, yellowish, pinkish.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: prismatic crystals, granular, massive.
Often confused with
Sellaite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Quartz is the harder of the two (Mohs 7 vs. 5).
How to tell apart: Sellaite is noticeably harder (Mohs 5 vs. 4).
How to tell apart: Luster reads vitreous on Sellaite and vitreous to pearly on Apophyllite.
Often found alongside sellaite
Minerals reported to co-occur with sellaite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- MgF₂
- Mohs hardness
- 5
- Density
- 3.17 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Tetragonal
- Crystal habit
- Prismatic Crystals, Granular, Massive
- Cleavage
- Perfect On {110}
- Rarity
- Rare
- Uses
- Collector, Research
- Host rock
- Hydrothermal Veins, Evaporite Deposits, Metamorphic Rocks
- Typical price
- $20-150 for small specimens
Where rockhounds find sellaite
Classic worldwide localities
- Ivigtut, Greenland
- Val di Susa, Italy
- Little Cottonwood Canyon, Utah, USA
- Guanajuato, Mexico
Field-hunting tip
Look in hydrothermal veins, evaporite deposits, metamorphic rocks country — that is the host setting where sellaite typically forms. If you start seeing fluorite, quartz, dolomite in float, you are in the right ground. Field specimens usually show a prismatic crystals, granular, massive habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find sellaite on the map
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