Oskarssonite is a rare aluminum fluoride mineral primarily found as a sublimation product in volcanic fumaroles. It typically occurs as small, delicate platy crystals and is often associated with other halide and sulfate minerals in active volcanic environments.

Hardness
1-2
Mohs
Luster
Vitreous
Streak
White
Transparency
Transparent

Is this oskarssonite?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

  • 1
    Test the hardness
    Try to scratch oskarssonite with a known reference. Oskarssonite sits at Mohs 1-2 — softer than the next harder reference, harder than the previous one.
  • 2
    Check the streak
    Drag the specimen across an unglazed porcelain plate. Oskarssonite leaves a white streak.
  • 3
    Read the luster
    Hold the specimen under a strong light. Oskarssonite typically shows a vitreous luster.
  • 4
    Match the color range
    Compare against the expected color range: white, colorless.
  • 5
    Look at form & habit
    Crystal system: trigonal. Typical habit: platy crystals, granular.

Often confused with

Oskarssonite vs. its common look-alikes — and how to tell them apart in the field.

Often found alongside oskarssonite

Minerals reported to co-occur with oskarssonite. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula
AlF₃
Mohs hardness
1-2
Density
2.47 g/cm³
Streak
White
Luster
Vitreous
Transparency
Transparent
Crystal system
Trigonal
Crystal habit
Platy Crystals, Granular
Cleavage
Perfect
Rarity
Rare
Uses
Collector
Host rock
Volcanic Fumaroles
Typical price
$50-500 depending on specimen quality

Where rockhounds find oskarssonite

Classic worldwide localities

  • Eldfell volcano, Heimaey, Iceland

Field-hunting tip

Look in volcanic fumaroles country — that is the host setting where oskarssonite typically forms. If you start seeing hematite, fluorite, anhydrite in float, you are in the right ground. Field specimens usually show a platy crystals, granular habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify oskarssonite?+
Mohs hardness is 1-2. It typically shows a vitreous luster. The streak is white. Common colors include white, colorless.
Where is oskarssonite found?+
Notable localities include Eldfell volcano, Heimaey, Iceland.
How much is oskarssonite worth?+
Typical asking prices fall in the range of $50-500 depending on specimen quality. Quality, size, and provenance can move individual specimens well outside that range.
What rocks look like oskarssonite?+
Oskarssonite is most often confused with Cryolite, Chiolite. A quick hardness test and a streak check separate the look-alikes faster than color alone.
What minerals are found with oskarssonite?+
Oskarssonite commonly co-occurs with hematite, fluorite, anhydrite. Spotting any of these in float or country rock is a useful trip signal.
What kind of rock does oskarssonite form in?+
Oskarssonite typically forms in volcanic fumaroles. Working float back to the host body is the standard way to chase a fresh occurrence.
What is oskarssonite used for?+
Oskarssonite is used in collector.

Find oskarssonite on the map

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