Muthmannite is a rare silver-gold telluride often found in epithermal gold deposits. It is typically identified in massive form within hydrothermal quartz veins, characterized by its metallic luster and high density.
Is this muthmannite?
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 muthmannite with a known reference. Muthmannite 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. Muthmannite leaves a black to gray-black streak.
- 3Read the lusterHold the specimen under a strong light. Muthmannite typically shows a metallic luster.
- 4Match the color rangeCompare against the expected color range: pale yellow, tin-white, grayish-white.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: massive, granular, or anhedral grains.
Often confused with
Muthmannite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Muthmannite leaves black to gray-black, Sylvanite leaves gray.
How to tell apart: Streak differs, so Muthmannite leaves black to gray-black, Calaverite leaves yellowish-green.
How to tell apart: Streak differs, so Muthmannite leaves black to gray-black, Petzite leaves iron-black.
Often found alongside muthmannite
Minerals reported to co-occur with muthmannite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- AgAuTe₂
- Mohs hardness
- 2.5
- Density
- 11.04 g/cm³
- Streak
- Black to Gray-black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Massive, Granular, Or Anhedral Grains
- Cleavage
- One Perfect, In Zone of Elongation
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Veins
Where rockhounds find muthmannite
Classic worldwide localities
- Sacaramb, Romania
- Kalgoorlie, Australia
- Crippled Creek, USA
Field-hunting tip
Look in hydrothermal veins country, the host setting where muthmannite typically forms. If you start seeing gold, tellurides, quartz in float, you are in the right ground. Field specimens usually show a massive, granular, or anhedral grains habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find muthmannite on the map
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