Ferrinatrite is a rare sodium iron sulfate mineral that typically forms as an efflorescence in the oxidized zones of arid mining districts. It is highly soluble in water, meaning collectors must keep specimens in a dry environment to prevent dehydration or degradation.
Is this ferrinatrite?
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 ferrinatrite with a known reference. Ferrinatrite 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.
- 4Match the color rangeCompare against the expected color range: white, pale green, bluish green, purplish, colorless.
- 5Look at form & habitCrystal system: trigonal. Typical habit: fibrous, spherical.
Often confused with
Ferrinatrite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Ferrinatrite leaves white, Copiapite leaves pale yellow; luster reads vitreous on Ferrinatrite and pearly on {010} on Copiapite.
How to tell apart: Luster reads vitreous on Ferrinatrite and pearly, silky in aggregates on Fibroferrite.
Often found alongside ferrinatrite
Minerals reported to co-occur with ferrinatrite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Na₃Fe(SO₄)₃·3H₂O
- Mohs hardness
- 2.5
- Density
- 2.55-2.61 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Trigonal
- Crystal habit
- Fibrous, spherical
- Cleavage
- On {1010}, perfect; on {1120}, less perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- An oxidation product of iron sulfides, typically in arid regions; rarely fumarolic
Where rockhounds find ferrinatrite
Classic worldwide localities
- Various localities in the Atacama Desert, Chile, as at Mina la Compania, near Sierra Gorda, Atacama
- Alcaparrosa, near Cerritos Bayos, southwest of Calama, from Quetena, west of Calama, and at Chuquicamata, Antofagasta
- Vesuvius, Campania, and at the Cetine mine, near Rosia, Tuscany, Italy
- Escuhu Formation, Teruel Province, and at the Lanjarón mineral springs, Granada Province, Spain
Field-hunting tip
Where it forms: An oxidation product of iron sulfides, typically in arid regions; rarely fumarolic. If you start seeing metavoltine, copiapite, coquimbite in float, you are in the right ground. Typical habit: fibrous, spherical. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify ferrinatrite?+
Where is ferrinatrite found?+
What rocks look like ferrinatrite?+
What minerals are found with ferrinatrite?+
What kind of rock does ferrinatrite form in?+
What is ferrinatrite used for?+
Find ferrinatrite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
