Gustavite is a rare lead-silver-bismuth sulfosalt that typically occurs as small, metallic lead-gray masses within hydrothermal sulfide deposits. It is often challenging to identify macroscopically and usually requires laboratory confirmation such as X-ray diffraction or chemical analysis to distinguish it from other lead-bismuth sulfosalts like lillianite.
Is this gustavite?
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 gustavite with a known reference. Gustavite sits at Mohs 3.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: gray.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: steel gray.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: tabular.
Often confused with
Gustavite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Gustavite is noticeably harder (Mohs 3.5 vs. 2.5-2.75); streak differs, so Gustavite leaves gray, Galena leaves lead-gray.
How to tell apart: Streak differs, so Gustavite leaves gray, Lillianite leaves black.
How to tell apart: Gustavite is noticeably harder (Mohs 3.5 vs. 2-2.5); streak differs, so Gustavite leaves gray, Bismuthinite leaves lead-gray.
Often found alongside gustavite
Minerals reported to co-occur with gustavite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- PbAgBi₃S₆
- Mohs hardness
- 3.5
- Density
- 7.01 g/cm³
- Colors
- Streak
- Gray
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Tabular
- Cleavage
- Rare, parallel to the tabular faces; even more rarely perpendicular to the tabular faces
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A rare mineral of hydrothermal origin; also in pegmatites
Where rockhounds find gustavite
Classic worldwide localities
- Silver Bell mine, Red Mountain district, Ouray Co., and at the Old Lout mine, Poughkeepsie Gulch, near Ouray, San Juan Co., Colorado, USA
- South Mountain, Owyhee Co., Idaho, USA
- Darwin, Inyo Co., and Randsburg, San Bernardino Co., California, USA
- Outlaw mine, about 17 km north of Manhattan, Round Mountain district, Nye Co., Nevada, USA
- Ivigtut cryolite deposit, southwestern Greenland (type locality)
- Terra Mining and Exploration Co., Camsell River, Northwest Territories, and from the Tanco pegmatite, Bernic Lake, Manitoba, Canada
Field-hunting tip
Where it forms: A rare mineral of hydrothermal origin; also in pegmatites. If you start seeing aikinite, bismuthinite, cosalite in float, you are in the right ground. Typical habit: tabular. Train your eye for that shape before scanning the outcrop.
Common questions
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Find gustavite on the map
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