Protochabournéite is an exceptionally rare sulfosalt mineral containing both thallium and arsenic. It is primarily found in hydrothermal deposits, often occurring as microscopic aggregates associated with other rare thallium minerals.
Is this protochabournéite?
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 protochabournéite with a known reference. Protochabournéite 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: black.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: black.
- 5Look at form & habitCrystal system: triclinic. Typical habit: anhedral grains, tabular aggregates.
Often confused with
Protochabournéite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Protochabournéite leaves black, Chabournéite leaves red-brown; luster reads metallic on Protochabournéite and submetallic to greasy on Chabournéite.
How to tell apart: Streak differs, so Protochabournéite leaves black, Realgar leaves red-orange to red; luster reads metallic on Protochabournéite and resinous to greasy on Realgar.
How to tell apart: Streak differs, so Protochabournéite leaves black, Orpiment leaves pale lemon-yellow; luster reads metallic on Protochabournéite and resinous, pearly on cleavage surface on Orpiment.
Often found alongside protochabournéite
Minerals reported to co-occur with protochabournéite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Tl₄-xPb₂+2xSb₂₀-x-yAsyS₃₄ (with 0.02 ≤ x ≤ 0.34, 5.71 ≤ y ≤ 6.69)
- Mohs hardness
- 2.5
- Density
- 5.008 g/cm³
- Colors
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Triclinic
- Crystal habit
- Anhedral grains, tabular aggregates
- Cleavage
- Imperfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In a metamorphosed barite-pyrite-magnetite-hematite deposit
Where rockhounds find protochabournéite
Classic worldwide localities
- Sant’Olga level of the Monte Arsiccio mine, near Sant’Anna di Stazzema, Apuan Alps, Tuscany, Italy
Field-hunting tip
Where it forms: In a metamorphosed barite-pyrite-magnetite-hematite deposit. If you start seeing barite, boscardinite, calcite in float, you are in the right ground. Typical habit: anhedral grains, tabular aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify protochabournéite?+
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What rocks look like protochabournéite?+
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Find protochabournéite on the map
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