Krausite is a rare potassium iron sulfate mineral that forms distinct, yellow, tabular monoclinic crystals. It is typically found in hyper-arid environments as a secondary mineral resulting from the alteration of iron-bearing sulfides. Collectors prize it for its rarity and its association with other colorful sulfate minerals.
Is this krausite?
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 krausite with a known reference. Krausite 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. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous to dull.
- 4Match the color rangeCompare against the expected color range: yellow green, light yellow, lemon.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic.
Often confused with
Krausite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Krausite leaves white, Jarosite leaves pale yellow; luster reads vitreous to dull on Krausite and subadamantine to vitreous, resinous on fractures on Jarosite.
How to tell apart: Streak differs, so Krausite leaves white, Copiapite leaves pale yellow; luster reads vitreous to dull on Krausite and pearly on {010} on Copiapite.
Often found alongside krausite
Minerals reported to co-occur with krausite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- KFe(SO₄)₂(H₂O)
- Mohs hardness
- 2.5
- Density
- 2.840 g/cm³
- Streak
- White
- Luster
- Vitreous to dull
- Transparency
- Transparent to opaque
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic
- Cleavage
- On {001}, perfect; on {100}, good
- Rarity
- Rare
- Uses
- Collector
- Host rock
- An uncommon secondary mineral in sulfate-bearing cherts (Borate, California, USA); formed on a dump by post-mine oxidation of pyrite (Velardeña mine, Mexico)
Where rockhounds find krausite
Classic worldwide localities
- Sulfur Hole prospect, near Borate, about 10 km northeast of Yermo, Calico Hills, San Bernardino Co., California, and in the Coral Reefs district, Wayne Co., Utah, USA
- Santa Maria mine, Velardeña, Durango, Mexico
- Santa Bárbara sulfur mine, El Palmar district, Jujuy Province, Argentina
- Campi Flegrei, near Naples, Campania, Italy
Field-hunting tip
Where it forms: An uncommon secondary mineral in sulfate-bearing cherts (Borate, California, USA); formed on a dump by post-mine oxidation of pyrite (Velardeña mine, Mexico). If you start seeing alunite, coquimbite, römerite in float, you are in the right ground. Typical habit: prismatic. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify krausite?+
Where is krausite found?+
What rocks look like krausite?+
What minerals are found with krausite?+
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Find krausite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
