Argentojarosite is a silver-bearing member of the jarosite group, typically forming as a secondary mineral in the oxidized zones of silver deposits. Collectors usually encounter it as fine-grained, earthy, or powdery crusts associated with other iron sulfates and lead minerals. It is identified by its distinct yellowish color and its presence in the supergene environment of mines.
Is this argentojarosite?
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 argentojarosite with a known reference. Argentojarosite 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. Argentojarosite leaves a pale yellow streak.
- 3Read the lusterHold the specimen under a strong light. Argentojarosite typically shows a dull luster.
- 4Match the color rangeCompare against the expected color range: yellow, yellowish-brown.
- 5Look at form & habitCrystal system: trigonal. Typical habit: microcrystalline crusts, massive, powdery coatings.
Often confused with
Argentojarosite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Argentojarosite leaves pale yellow, Jarosite leaves yellow; luster reads dull on Argentojarosite and vitreous on Jarosite.
How to tell apart: Streak differs — Argentojarosite leaves pale yellow, Natrojarosite leaves yellow.
How to tell apart: Streak differs — Argentojarosite leaves pale yellow, Limonite leaves yellowish-brown; luster reads dull on Argentojarosite and submetallic to earthy on Limonite.
Often found alongside argentojarosite
Minerals reported to co-occur with argentojarosite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- AgFe₃(SO₄)₂(OH)₆
- Mohs hardness
- 2.5-3.5
- Density
- 3.7-3.9 g/cm³
- Colors
- Streak
- Pale Yellow
- Luster
- Dull
- Transparency
- Opaque
- Crystal system
- Trigonal
- Crystal habit
- Microcrystalline Crusts, Massive, Powdery Coatings
- Cleavage
- None
- Rarity
- Uncommon
- Uses
- Collector, Scientific Research
- Host rock
- Oxidized Zones of Silver-rich Ore Deposits
- Typical price
- $20-150 for mineral specimens depending on quality and locality
Where rockhounds find argentojarosite
Classic worldwide localities
- Silver King Mine, Arizona, USA
- Chañarcillo, Chile
- Broken Hill, Australia
- Tsumeb, Namibia
Field-hunting tip
Look in oxidized zones of silver-rich ore deposits country — that is the host setting where argentojarosite typically forms. If you start seeing jarosite, limonite, anglesite in float, you are in the right ground. Field specimens usually show a microcrystalline crusts, massive, powdery coatings habit, so train your eye for that shape before scanning the outcrop.
Common questions
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