Montbrayite is a rare gold-telluride mineral typically found as massive aggregates within hydrothermal ore deposits. It is best identified by its high density and association with other telluride species, often requiring X-ray diffraction for definitive confirmation.
Is this montbrayite?
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 montbrayite with a known reference. Montbrayite 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: white.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: yellowish white, light yellow, tin white.
- 5Look at form & habitCrystal system: triclinic. Typical habit: irregular grains.
Often confused with
Montbrayite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Montbrayite leaves white, Petzite leaves grayish black.
How to tell apart: Streak differs, so Montbrayite leaves white, Krennerite leaves greenish gray; luster reads metallic on Montbrayite and very high metallic on Krennerite.
How to tell apart: Streak differs, so Montbrayite leaves white, Calaverite leaves greenish to yellowish gray.
Often found alongside montbrayite
Minerals reported to co-occur with montbrayite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Au,Ag,Sb,Bi,Pb)₂₃(Te,Sb,Bi,Pb)₃₈
- Mohs hardness
- 2.5
- Density
- 9.94 g/cm³
- Streak
- White
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Triclinic
- Crystal habit
- Irregular grains
- Cleavage
- {110}, {011}, {111}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- With other tellurides, sulfides, and gold in coarsely crystalline masses almost free from gangue (Robb-Montbray mine, Canada)
Where rockhounds find montbrayite
Classic worldwide localities
- April Fool mine, Delamar district, Lincoln Co., Nevada, USA
- Robb-Montbray mine, Montbray Township, Quebec, Canada (type locality)
- Voronezhskiy massif, 50 km south of Orel, Russia
- Enasen, Sweden
- Musariu, Romania
- Kalgoorlie, Western Australia
Field-hunting tip
Where it forms: With other tellurides, sulfides, and gold in coarsely crystalline masses almost free from gangue (Robb-Montbray mine, Canada). If you start seeing calaverite, gold, tellurobismuthite in float, you are in the right ground. Typical habit: irregular grains. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify montbrayite?+
Where is montbrayite found?+
Is montbrayite safe to handle?+
What rocks look like montbrayite?+
What minerals are found with montbrayite?+
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Find montbrayite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
