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, so 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, so 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, 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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