Robinsonite is a rare lead antimony sulfosalt that typically occurs as fibrous to needle-like gray aggregates in hydrothermal environments. It is often visually indistinguishable from other lead-antimony sulfosalts like jamesonite without formal analytical verification like X-ray diffraction. Collectors value it as an elusive species found primarily in complex sulfide deposit zones.
Is this robinsonite?
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 robinsonite with a known reference. Robinsonite sits at Mohs 2.5-3, 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: bluish lead gray.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: massive, prismatic, striated.
Often confused with
Robinsonite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside robinsonite
Minerals reported to co-occur with robinsonite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Pb₄Sb₆S₁₃
- Mohs hardness
- 2.5-3
- Density
- 5.64-5.75 g/cm³
- Colors
- Bluish lead gray
- Streak
- Gray
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Massive, prismatic, striated
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A primary hydrothermal mineral with other lead sulfosalts
Where rockhounds find robinsonite
Classic worldwide localities
- Red Bird mercury mine, about 37 road km east of Lovelock, Antelope district, Pershing Co. (type locality), and in the Silver Coin mine, near Valmy, Iron Point district, Humboldt Co., Nevada, USA
- Cleary prospect, Fairbanks district, Alaska, USA
- Madoc, Ontario, and in the Dodger tungsten mine, Salmo, British Columbia, Canada
- Vall de Ribes, eastern Pyrenees, Spain
- Malé Železné and Däbrava deposits, Low Tatra Mountains, Slovakia
- Rujevac Sb–Zn–Pb deposit, western Serbia
Field-hunting tip
Where it forms: A primary hydrothermal mineral with other lead sulfosalts. If you start seeing zinkenite, boulangerite, semseyite in float, you are in the right ground. Typical habit: massive, prismatic, striated. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify robinsonite?+
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What rocks look like robinsonite?+
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Find robinsonite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
