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, 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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