Sterryite is a rare lead-silver sulfosalt mineral primarily known for its distinct acicular or fibrous habit. It is found in hydrothermal vein deposits and is most famously associated with the type locality in Madoc, Ontario, where it forms delicate gray-black aggregates.
Is this sterryite?
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 sterryite with a known reference. Sterryite 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. Sterryite leaves a black streak.
- 3Read the lusterHold the specimen under a strong light. Sterryite typically shows a metallic luster.
- 4Match the color rangeCompare against the expected color range: lead-gray, black.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: acicular to fibrous crystals, often as compact aggregates.
Often confused with
Sterryite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Sterryite is noticeably harder (Mohs 3.5 vs. 2.5); streak differs — Sterryite leaves black, Jamesonite leaves gray-black.
How to tell apart: Streak differs — Sterryite leaves black, Boulangerite leaves brownish-gray.
How to tell apart: Streak differs — Sterryite leaves black, Bournonite leaves steel-gray.
Often found alongside sterryite
Minerals reported to co-occur with sterryite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Pb₂₀Ag₃As₁₉S₄₈
- Mohs hardness
- 3.5
- Density
- 6.05 g/cm³
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Acicular to Fibrous Crystals, Often as Compact Aggregates
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Veins
- Typical price
- $50-300 per specimen
Where rockhounds find sterryite
Classic worldwide localities
- Madoc, Ontario, Canada
- Kutná Hora, Czech Republic
Field-hunting tip
Look in hydrothermal veins country — that is the host setting where sterryite typically forms. If you start seeing galena, sphalerite, arsenopyrite in float, you are in the right ground. Field specimens usually show a acicular to fibrous crystals, often as compact aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find sterryite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
