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. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: earthy.
- 4Match the color rangeCompare against the expected color range: white.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: earthy, nodular.
Often confused with
Lannonite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads earthy on Lannonite and subvitreous, pearly on {010} cleavages, silky if fibrous on Gypsum.
How to tell apart: Thaumasite is the harder of the two (Mohs 3.5 vs. 2); luster reads earthy on Lannonite and vitreous to dull, greasy, silky on Thaumasite.
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
- HCa₄Mg₂Al₄(SO₄)₈F₉·32H₂O
- Mohs hardness
- 2
- Density
- 2.22 g/cm³
- Colors
- Streak
- White
- Luster
- Earthy
- Transparency
- Semitransparent
- Crystal system
- Tetragonal
- Crystal habit
- Earthy, nodular
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A rare post-mine mineral deposited from solutions derived from an oxidizing breccia zone
Where rockhounds find lannonite
Classic worldwide localities
- Lone Pine mine, Wilcox district, near Silver City, Catron Co., New Mexico, USA
Field-hunting tip
Where it forms: A rare post-mine mineral deposited from solutions derived from an oxidizing breccia zone. If you start seeing fluorite, gypsum, khademite in float, you are in the right ground. Typical habit: earthy, nodular. 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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