Iodargyrite is a rare silver halide mineral that forms in the oxidized zones of silver deposits. It typically appears as thin, yellowish, waxy-looking tabular crystals or coatings on other minerals and is highly prized by collectors for its role as a primary silver mineral.
Is this iodargyrite?
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 iodargyrite with a known reference. Iodargyrite sits at Mohs 1.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: yellow, shining.
- 3Read the lusterHold the specimen under a strong light. Luster: resinous to adamantine, pearly on cleavage surfaces.
- 4Match the color rangeCompare against the expected color range: yellow, colorless, pale yellow, greenish yellow, gray.
- 5Look at form & habitCrystal system: hexagonal. Typical habit: platy.
Often confused with
Iodargyrite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Chlorargyrite is the harder of the two (Mohs 2.5 vs. 1.5); streak differs, so Iodargyrite leaves yellow, shining, Chlorargyrite leaves white.
How to tell apart: Bromargyrite is the harder of the two (Mohs 2.5 vs. 1.5); streak differs, so Iodargyrite leaves yellow, shining, Bromargyrite leaves white to yellowish white.
Often found alongside iodargyrite
Minerals reported to co-occur with iodargyrite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- AgI
- Mohs hardness
- 1.5
- Density
- 5.69 g/cm³
- Streak
- Yellow, shining
- Luster
- Resinous to adamantine, pearly on cleavage surfaces
- Transparency
- Transparent
- Crystal system
- Hexagonal
- Crystal habit
- Platy
- Cleavage
- {0001}, perfect
- Rarity
- Rare
- Uses
- Collector, Scientific research
- Host rock
- A secondary mineral in the oxidized portions of silver-bearing deposits
Where rockhounds find iodargyrite
Classic worldwide localities
- Tonopah, Nye Co., and Goldfield, Esmeralda Co., Nevada, USA
- Lake Valley, Sierra Co., New Mexico, USA
- Commonwealth mine, Pearce, Cochise Co., Arizona, USA
- Abarradón, near Mazapil, Zacatecas, Mexico
- Chañarcillo, south of Copiapó, Atacama, Chile
- Caracoles, Sierra Gorda district, Antofagasta, Chile
Field-hunting tip
Where it forms: A secondary mineral in the oxidized portions of silver-bearing deposits. If you start seeing silver, acanthite, chlorargyrite in float, you are in the right ground. Typical habit: platy. Train your eye for that shape before scanning the outcrop.
Common questions
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Find iodargyrite on the map
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