Benleonardite is a rare silver sulfotelluride typically found as thin, dark blue-to-black coatings on other minerals in hydrothermal deposits. It is best identified through laboratory analysis of its metallic, opaque character and specific paragenesis in rare tellurium-rich ore bodies.
Is this benleonardite?
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 benleonardite with a known reference. Benleonardite 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. Streak: black.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: gray, black.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: anhedral grains, microscopic crystals.
Often confused with
Benleonardite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside benleonardite
Minerals reported to co-occur with benleonardite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ag₁₅Cu(Sb,As)₂S₇Te₄
- Mohs hardness
- 3.5
- Density
- 7.76 g/cm³
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Tetragonal
- Crystal habit
- Anhedral grains, microscopic crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In fractures in an intensely silicified rhyolitic vitrophyre (Moctezuma mine, Mexico); in a limestone-hosted disseminated Au–Ag–Te deposit (Mayflower mine, Montana, USA)
Where rockhounds find benleonardite
Classic worldwide localities
- Mayflower mine, Tobacco Root Mountains, Madison Co., and the Gies mine, Judith Mountains, Fergus Co., Montana, USA
- Moctezuma (Bambolla) mine, 12 km south of Moctezuma, Sonora, Mexico (type locality)
- Emperor mine, Vatukoula, and the Tuvatu Au–Ag–Te deposit, Viti Levu, Fiji Islands
Field-hunting tip
Where it forms: In fractures in an intensely silicified rhyolitic vitrophyre (Moctezuma mine, Mexico); in a limestone-hosted disseminated Au–Ag–Te deposit (Mayflower mine, Montana, USA). If you start seeing silver, acanthite, hessite in float, you are in the right ground. Typical habit: anhedral grains, microscopic crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify benleonardite?+
Where is benleonardite found?+
Is benleonardite safe to handle?+
What rocks look like benleonardite?+
What minerals are found with benleonardite?+
What kind of rock does benleonardite form in?+
What is benleonardite used for?+
Find benleonardite on the map
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