Lanmuchangite is a very rare aluminum sulfate mineral typically found as white, needle-like or fibrous coatings on mine walls. It is primarily known from its type locality in the Lanmuchang deposit of China, where it forms in association with cinnabar and other hydrothermal minerals. Collectors should handle specimens with care due to their delicate, friable, and water-soluble nature.
Is this lanmuchangite?
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 lanmuchangite with a known reference. Lanmuchangite sits at Mohs 2.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Lanmuchangite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Lanmuchangite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, colorless.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: acicular crystals, fibrous efflorescences, radial aggregates.
Often confused with
Lanmuchangite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside lanmuchangite
Minerals reported to co-occur with lanmuchangite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Al₂SO₄(OH)₄·5H₂O
- Mohs hardness
- 2.5
- Density
- 1.79 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Acicular Crystals, Fibrous Efflorescences, Radial Aggregates
- Cleavage
- Perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Mercury-thallium Deposits
- Typical price
- $50-300 per specimen
Where rockhounds find lanmuchangite
Classic worldwide localities
- Lanmuchang mercury-thallium deposit, Guizhou Province, China
Field-hunting tip
Look in hydrothermal mercury-thallium deposits country — that is the host setting where lanmuchangite typically forms. If you start seeing quartz, cinnabar, calcite in float, you are in the right ground. Field specimens usually show a acicular crystals, fibrous efflorescences, radial aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find lanmuchangite on the map
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