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, so Madocite leaves black, Galena leaves lead-gray.
How to tell apart: Madocite is noticeably harder (Mohs 3.5 vs. 2.5); streak differs, so Madocite leaves black, Jamesonite leaves gray-black.
How to tell apart: Streak differs, so 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, 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.
