Amarantite is a rare hydrated iron sulfate typically found as a secondary mineral in the oxidized zones of iron-rich sulfide deposits. Collectors should look for its distinctive deep orange-red tabular crystals often forming subparallel, sheaf-like aggregates.
Is this amarantite?
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 amarantite with a known reference. Amarantite 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: lemon-yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: brown red, orange red, pink, red.
- 5Look at form & habitCrystal system: triclinic. Typical habit: tabular crystals, subparallel aggregates, drusy coatings.
Often confused with
Amarantite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Amarantite leaves lemon-yellow, Fibroferrite leaves white; luster reads vitreous on Amarantite and pearly, silky in aggregates on Fibroferrite.
How to tell apart: Streak differs, so Amarantite leaves lemon-yellow, Copiapite leaves pale yellow; luster reads vitreous on Amarantite and pearly on {010} on Copiapite.
How to tell apart: Streak differs, so Amarantite leaves lemon-yellow, Metahohmannite leaves light yellow.
Often found alongside amarantite
Minerals reported to co-occur with amarantite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Fe₂O(SO₄)₂·7H₂O
- Mohs hardness
- 2.5
- Density
- 2.189-2.286 g/cm³
- Streak
- Lemon-yellow
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Triclinic
- Crystal habit
- Tabular crystals, subparallel aggregates, drusy coatings
- Cleavage
- Perfect on {010} and {100}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A secondary mineral formed especially in arid climates
Where rockhounds find amarantite
Classic worldwide localities
- Santa Maria Mountains, Riverside Co., California, USA
- Antofagasta, from the Union mine, Reventon district, near Paposo, at the Compania mine, east of Sierra Gorda, Chile
- Quetena, west of Calama, Alcaparrosa, near Cerritos Bayos, southwest of Calama, and at Chuquicamata, Chile
- Tierra Amarilla, southeast of Copiapó, Atacama, Chile
- Saghand, Yazd, Iran
Field-hunting tip
Where it forms: A secondary mineral formed especially in arid climates. If you start seeing hohmannite, fibroferrite, chalcanthite in float, you are in the right ground. Typical habit: tabular crystals, subparallel aggregates, drusy coatings. Train your eye for that shape before scanning the outcrop.
Common questions
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Find amarantite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
