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 3.5-4.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: adamantine.
- 4Match the color rangeCompare against the expected color range: yellow, brown, yellow brown.
- 5Look at form & habitCrystal system: trigonal. Typical habit: micaceous.
Often confused with
Argentojarosite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Argentojarosite leaves yellow, Jarosite leaves pale yellow; luster reads adamantine on Argentojarosite and subadamantine to vitreous, resinous on fractures on Jarosite.
How to tell apart: Streak differs, so Argentojarosite leaves yellow, Natrojarosite leaves light yellow; luster reads adamantine on Argentojarosite and vitreous on Natrojarosite.
How to tell apart: Streak differs, so Argentojarosite leaves yellow, Limonite leaves yellowish-brown; luster reads adamantine 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
- 3.5-4.5
- Density
- 3.66 g/cm³
- Colors
- Streak
- Yellow
- Luster
- Adamantine
- Transparency
- Transparent to translucent
- Crystal system
- Trigonal
- Crystal habit
- Micaceous
- Cleavage
- On {0001}, distinct
- Rarity
- Uncommon
- Uses
- Collector, Scientific research
- Host rock
- An uncommon secondary mineral in the oxidized portions of silver- and sulfide-bearing mineral deposits
Where rockhounds find argentojarosite
Classic worldwide localities
- Tintic Standard mine, near Dividend, East Tintic district, Utah Co., USA
- Philadelphia mine, Organ district, Doña Ana Co., New Mexico, USA
- Cactus Queen mine, Kern Co., California, USA
- Santa Ana mine, Caborca, Sonora, Mexico
- West Turf Pits mine, Grassington Moor, Yorkshire, England
- Treore mine, St. Teath, and at Wheal Ludcott, St. Ives, Cornwall, England
Field-hunting tip
Where it forms: An uncommon secondary mineral in the oxidized portions of silver- and sulfide-bearing mineral deposits. If you start seeing anglesite, barite, quartz in float, you are in the right ground. Typical habit: micaceous. Train your eye for that shape before scanning the outcrop.
Common questions
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Find argentojarosite on the map
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