Sideronatrite is a rare hydrated sodium iron sulfate that typically forms as bright yellow fibrous or crusty aggregates. It is most commonly found in the extremely arid environments of the Atacama Desert in Chile, where it results from the weathering of iron sulfides.
Is this sideronatrite?
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 sideronatrite with a known reference. Sideronatrite 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. Sideronatrite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Sideronatrite typically shows a pearly luster.
- 4Match the color rangeCompare against the expected color range: yellow, pale yellow, golden yellow.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: fibrous, acicular, or encrusting masses.
Often confused with
Sideronatrite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Sideronatrite leaves white, Copiapite leaves yellow.
How to tell apart: Streak differs — Sideronatrite leaves white, Amarantite leaves yellowish-orange; luster reads pearly on Sideronatrite and vitreous on Amarantite.
Often found alongside sideronatrite
Minerals reported to co-occur with sideronatrite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Na₂Fe(SO₄)₂(OH)·3H₂O
- Mohs hardness
- 2.5
- Density
- 2.35 g/cm³
- Streak
- White
- Luster
- Pearly
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Fibrous, Acicular, Or Encrusting Masses
- Cleavage
- Perfect On {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Zones of Hydrothermal Sulfide Deposits
- Typical price
- $20-150 per specimen depending on size and quality
Where rockhounds find sideronatrite
Classic worldwide localities
- Chuquicamata, Chile
- Sierra Gorda, Chile
- Antofagasta, Chile
- Alcaparrosa, Chile
Field-hunting tip
Look in oxidized zones of hydrothermal sulfide deposits country — that is the host setting where sideronatrite typically forms. If you start seeing copiapite, coquimbite, jarosite in float, you are in the right ground. Field specimens usually show a fibrous, acicular, or encrusting masses habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify sideronatrite?+
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What rocks look like sideronatrite?+
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Find sideronatrite on the map
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