Halotrichite is a secondary sulfate mineral that typically forms as delicate, silky, fibrous efflorescences or crusts in the vicinity of weathering sulfide deposits. Due to its high water content and solubility, specimens should be stored in a dry, sealed environment to prevent dehydration and crumbling.
Is this halotrichite?
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 halotrichite with a known reference. Halotrichite 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. Halotrichite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Halotrichite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: colorless, white, yellow, yellowish-green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: fibrous, acicular, silky masses, efflorescent crusts.
Often confused with
Halotrichite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside halotrichite
Minerals reported to co-occur with halotrichite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- FeAl₂(SO₄)₄·22H₂O
- Mohs hardness
- 2
- Density
- 1.7-1.9 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Fibrous, Acicular, Silky Masses, Efflorescent Crusts
- Cleavage
- None
- Rarity
- Common
- Uses
- Collector
- Host rock
- Oxidized Zones of Sulfide Ore Deposits, Volcanic Fumaroles, Mine Dumps
- Typical price
- $10-40 per specimen
Where rockhounds find halotrichite
1 mapped spotsClassic worldwide localities
- Germany
- Hungary
- USA
- Chile
- Mexico
Field-hunting tip
Look in oxidized zones of sulfide ore deposits, volcanic fumaroles, mine dumps country — that is the host setting where halotrichite typically forms. If you start seeing melanterite, gypsum, jarosite in float, you are in the right ground. Field specimens usually show a fibrous, acicular, silky masses, efflorescent crusts habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Missouri — start trip planning there.
Common questions
How do you identify halotrichite?+
Where is halotrichite found?+
Can I find halotrichite in the United States?+
How much is halotrichite worth?+
What rocks look like halotrichite?+
What minerals are found with halotrichite?+
What kind of rock does halotrichite form in?+
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Find halotrichite on the map
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