Natrojarosite is a secondary mineral commonly found in the oxidized zones of metal-rich sulfide deposits. It typically forms as bright yellow earthy crusts or powdery masses that are easily mistaken for jarosite or limonite.
Is this natrojarosite?
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 natrojarosite with a known reference. Natrojarosite sits at Mohs 2.5-3.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Natrojarosite leaves a yellow streak.
- 3Read the lusterHold the specimen under a strong light. Natrojarosite typically shows a dull luster.
- 4Match the color rangeCompare against the expected color range: yellow, yellow-brown, golden-yellow.
- 5Look at form & habitCrystal system: trigonal. Typical habit: crusts, massive, earthy, pulverulent.
Often confused with
Natrojarosite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Luster reads dull on Natrojarosite and vitreous on Jarosite.
How to tell apart: Iron Ore is the harder of the two (Mohs 5-6.5 vs. 2.5-3.5); streak differs — Natrojarosite leaves yellow, Iron Ore leaves reddish-brown to black; luster reads dull on Natrojarosite and metallic to submetallic on Iron Ore.
How to tell apart: Streak differs — Natrojarosite leaves yellow, Limonite leaves yellowish-brown; luster reads dull on Natrojarosite and submetallic to earthy on Limonite.
Often found alongside natrojarosite
Minerals reported to co-occur with natrojarosite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaFe₃(SO₄)₂(OH)₆
- Mohs hardness
- 2.5-3.5
- Density
- 3.2-3.3 g/cm³
- Streak
- Yellow
- Luster
- Dull
- Transparency
- Opaque
- Crystal system
- Trigonal
- Crystal habit
- Crusts, Massive, Earthy, Pulverulent
- Cleavage
- None
- Rarity
- Common
- Uses
- Collector, Research
- Host rock
- Oxidized Zones of Hydrothermal Sulfide Deposits
- Typical price
- $10-50 thumbnail
Where rockhounds find natrojarosite
Classic worldwide localities
- Rio Tinto, Spain
- Black Pine mine, USA
- Chuquicamata, Chile
- Tintic district, USA
Field-hunting tip
Look in oxidized zones of hydrothermal sulfide deposits country — that is the host setting where natrojarosite typically forms. If you start seeing jarosite, gypsum, goethite in float, you are in the right ground. Field specimens usually show a crusts, massive, earthy, pulverulent habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find natrojarosite on the map
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