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 5-5.5, 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: tetragonal. Typical habit: prismatic.
Often confused with
Sellaite vs. its common look-alikes, and how to tell them apart in the field.
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
- 5-5.5
- Density
- 3.15 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Tetragonal
- Crystal habit
- Prismatic
- Cleavage
- Perfect on {010} and {110}
- Rarity
- Rare
- Uses
- Collector, Research
- Host rock
- In a bituminous dolomite-anhydrite rock (Gebroulaz glacier, France); in evaporites (Bleicherode, Germany); in volcanic ejecta and fumarolic deposits (Vesuvius, Italy); in marble (Carrara, Italy)
Where rockhounds find sellaite
Classic worldwide localities
- Rico-Argentine mine group, Rico district, Dolores Co., Colorado, USA
- Moraine of the Gebroulaz glacier, near Moûtiers, Savoy, and in the Font Sante mine, Estrel, Var, France
- Bleicherode, Harz, in the Clara mine, near Oberwolfach, Black Forest, and at Emmelberg, Eifel district, Germany
- Carrara, Tuscany, Italy
- Vesuvius, Campania, and on Mt. Etna, Sicily, Italy
- Lake Gjerdingen, Nordmarka, Norway
Field-hunting tip
Where it forms: In a bituminous dolomite-anhydrite rock (Gebroulaz glacier, France); in evaporites (Bleicherode, Germany); in volcanic ejecta and fumarolic deposits (Vesuvius, Italy); in marble (Carrara, Italy). If you start seeing fluorite, sulfur, celestine in float, you are in the right ground. Typical habit: prismatic. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify sellaite?+
Where is sellaite found?+
What rocks look like sellaite?+
What minerals are found with sellaite?+
What kind of rock does sellaite form in?+
What is sellaite used for?+
Find sellaite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
