Lannonite is a very rare hydrated calcium potassium sulfate fluoride mineral that typically forms delicate, fibrous, or radiating crusts within dolomite vugs. It was first described from the Lannon Quarry in Wisconsin and is highly sought after by systematic mineral collectors. Due to its solubility and fragile nature, specimens should be handled with care and stored in a humidity-controlled environment.
Is this lannonite?
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 lannonite with a known reference. Lannonite sits at Mohs 2 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Lannonite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Lannonite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, colorless.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: fibrous or acicular crusts and radiating tufts.
Often confused with
Lannonite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside lannonite
Minerals reported to co-occur with lannonite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- H₂KCa₂(SO₄)₃F·H₂O
- Mohs hardness
- 2
- Density
- 1.89 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Fibrous or Acicular Crusts and Radiating Tufts
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Dolomite Vugs
- Typical price
- $50-200 for micro specimens
Where rockhounds find lannonite
Classic worldwide localities
- Lannon Quarry, Waukesha County, Wisconsin, USA
Field-hunting tip
Look in dolomite vugs country — that is the host setting where lannonite typically forms. If you start seeing dolomite, gypsum, celestine in float, you are in the right ground. Field specimens usually show a fibrous or acicular crusts and radiating tufts habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find lannonite on the map
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