Madocite is a very rare lead-antimony sulfosalt known primarily from its type locality in Ontario. Collectors typically find it as dark, metallic grains associated with galena in dolomite veins, requiring microscopic or X-ray identification due to its similarity to other lead sulfosalts.
Is this madocite?
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 madocite with a known reference. Madocite 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. Madocite leaves a black streak.
- 3Read the lusterHold the specimen under a strong light. Madocite 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: anhedral to subhedral grains, massive.
Often confused with
Madocite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Madocite is noticeably harder (Mohs 3.5 vs. 2.5); streak differs — Madocite leaves black, Galena leaves lead-gray.
How to tell apart: Madocite is noticeably harder (Mohs 3.5 vs. 2.5); streak differs — Madocite leaves black, Jamesonite leaves gray-black.
How to tell apart: Streak differs — Madocite leaves black, Bournonite leaves steel-gray.
Often found alongside madocite
Minerals reported to co-occur with madocite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Pb₁₇Sb₁₆S₃₅
- Mohs hardness
- 3.5
- Density
- 5.68 g/cm³
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Anhedral to Subhedral Grains, Massive
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Veins in Limestone
- Typical price
- $50-300 per specimen
Where rockhounds find madocite
Classic worldwide localities
- Madoc, Ontario, Canada
Field-hunting tip
Look in hydrothermal veins in limestone country — that is the host setting where madocite typically forms. If you start seeing galena, dolomite, quartz in float, you are in the right ground. Field specimens usually show a anhedral to subhedral grains, massive habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find madocite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
