Matildite is a silver bismuth sulfide mineral frequently found in complex intergrowths with galena, often formed through the exsolution of silver-rich galena as it cools. Collectors typically find it as massive, metallic-gray blebs within sulfide ore deposits. It is best identified by its high density and metallic luster, often requiring microscopic examination to distinguish from associated sulfide species.
Is this matildite?
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 matildite with a known reference. Matildite sits at Mohs 2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: pale gray.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: gray, iron black.
- 5Look at form & habitCrystal system: trigonal. Typical habit: acicular, massive.
Often confused with
Matildite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Matildite leaves pale gray, Galena leaves lead-gray.
How to tell apart: Streak differs, so Matildite leaves pale gray, Bismuthinite leaves lead-gray.
How to tell apart: Streak differs, so Matildite leaves pale gray, Acanthite leaves black.
Often found alongside matildite
Minerals reported to co-occur with matildite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- AgBiS₂
- Mohs hardness
- 2.5
- Density
- 6.9 g/cm³
- Colors
- Streak
- Pale gray
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Trigonal
- Crystal habit
- Acicular, massive
- Cleavage
- None
- Rarity
- Uncommon
- Uses
- Collector, Scientific study
- Host rock
- Formed in hydrothermal deposits at medium to high temperatures and in pegmatites
Where rockhounds find matildite
Classic worldwide localities
- Mayflower mine, Boise basin area, Ada Co., Idaho, USA
- Darwin mine, Inyo Co., California, USA
- Lake City, Hinsdale Co., in the Revell #1 mine, north of Silver Cliff, Custer Co., at Leadville, Lake Co., Colorado, USA
- Campbell mine, Bisbee, Cochise Co., Arizona, USA
- Matilda mine, near Morococha, Peru (type locality)
- Cerro Rico, Potosí, Bolivia
Field-hunting tip
Where it forms: Formed in hydrothermal deposits at medium to high temperatures and in pegmatites. If you start seeing galena, pavonite, aikinite in float, you are in the right ground. Typical habit: acicular, massive. Train your eye for that shape before scanning the outcrop.
Common questions
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Find matildite on the map
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