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, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: gray-black, shining.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: grayish black.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: crystalline, striated.
Often confused with
Madocite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Madocite leaves gray-black, shining, Galena leaves lead-gray.
How to tell apart: Streak differs, so Madocite leaves gray-black, shining, Jamesonite leaves black. grayish.
How to tell apart: Streak differs, so Madocite leaves gray-black, shining, Bournonite leaves steel-gray to iron-black; luster reads metallic on Madocite and brilliant to dull on Bournonite.
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
- Pb₁₉(Sb,As)₁₆S₄₃
- Mohs hardness
- 3
- Density
- 5.98 g/cm³
- Colors
- Streak
- Gray-black, shining
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Crystalline, striated
- Cleavage
- Perfect on {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In the marbles of the Precambrian Grenville Limestone, at the margin of an intrusive (Madoc, Canada); in a hydrothermal deposit in dolomitic limestones with other As–Tl minerals (Jas Roux, France)
Where rockhounds find madocite
Classic worldwide localities
- Madoc, Huntington Township, Ontario, Canada (type locality)
- Jas Roux deposit, 10 km east of Chapelle-en-Valgaudemar, Hautes-Alpes, France
- Novoye, Khaydarkan, Fergana Valley, Alai Range, Kyrgyzstan
- Boliden, Västerbotten, Sweden
- Colquiri, Bolivia
Field-hunting tip
Where it forms: In the marbles of the Precambrian Grenville Limestone, at the margin of an intrusive (Madoc, Canada); in a hydrothermal deposit in dolomitic limestones with other As–Tl minerals (Jas Roux, France). If you start seeing jamesonite, boulangerite, arsnopyrite in float, you are in the right ground. Typical habit: crystalline, striated. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify madocite?+
Where is madocite found?+
Is madocite safe to handle?+
What rocks look like madocite?+
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Find madocite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
