Joséite-A is a rare bismuth telluride sulfide that typically occurs as metallic, lead-gray tabular crystals or foliated masses. It is most often found within hydrothermal gold deposits, frequently associated with other rare tellurides and native bismuth. Collectors usually prize it for its association with native gold and its distinct metallic luster.
Is this joséite-a?
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 joséite-a with a known reference. Joséite-A sits at Mohs 2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: black-gray.
- 3Read the lusterHold the specimen under a strong light. Luster: high metallic, tarnishing lead-gray, iridescent, steel-blue to iron-black.
- 4Match the color rangeCompare against the expected color range: silver-white.
- 5Look at form & habitCrystal system: trigonal. Typical habit: tabular crystals, foliated masses, or lamellar grains.
Often confused with
Joséite-A vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Joséite-A leaves black-gray, Bismuthinite leaves lead-gray; luster reads high metallic, tarnishing lead-gray, iridescent, steel-blue to iron-black on Joséite-A and metallic on Bismuthinite.
How to tell apart: Streak differs, so Joséite-A leaves black-gray, Tetradymite leaves pale steel-gray; luster reads high metallic, tarnishing lead-gray, iridescent, steel-blue to iron-black on Joséite-A and metallic, splendent on fresh surfaces on Tetradymite.
How to tell apart: Streak differs, so Joséite-A leaves black-gray, Tellurobismuthite leaves pale lead-gray; luster reads high metallic, tarnishing lead-gray, iridescent, steel-blue to iron-black on Joséite-A and metallic, splendent on fresh cleavages on Tellurobismuthite.
Often found alongside joséite-a
Minerals reported to co-occur with joséite-a. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Bi₄TeS₂
- Mohs hardness
- 2
- Density
- 8.18 g/cm³
- Colors
- Streak
- Black-gray
- Luster
- High metallic, tarnishing lead-gray, iridescent, steel-blue to iron-black
- Transparency
- Opaque
- Crystal system
- Trigonal
- Crystal habit
- Tabular crystals, foliated masses, or lamellar grains
- Cleavage
- {0001}, perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In bismuth-rich hydrothermal deposits
Where rockhounds find joséite-a
Classic worldwide localities
- San José, near Marianna, Minas Gerais, Brazil (type locality)
- Glacier Gulch, Hudson Bay Mountain, near Smithers, Canada
- Windpass mine, near Chu Chua, British Columbia, Canada
- Territory, from placers in Clear Creek, McQuesten district, and in Highet Creek, Mayo district, Yukon, Canada
- Serrania de Ronda, Málaga Province, Spain
- Carrock mine, Caldbeck Fells, and the Coniston mines, Cumbria, and at Penlee Quarry, Cornwall, England
Field-hunting tip
Where it forms: In bismuth-rich hydrothermal deposits. If you start seeing gold, bismuth, bismuthinite in float, you are in the right ground. Typical habit: tabular crystals, foliated masses, or lamellar grains. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify joséite-a?+
Where is joséite-a found?+
Is joséite-a safe to handle?+
What rocks look like joséite-a?+
What minerals are found with joséite-a?+
What kind of rock does joséite-a form in?+
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Find joséite-a on the map
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