Avicennite is an extremely rare thallium oxide mineral that typically occurs as tiny, metallic black grains within hydrothermal ore deposits. It is named in honor of the Persian philosopher Avicenna (Ibn Sina). Due to its high thallium content and scarcity, it is highly sought after by advanced systematic mineral collectors.
Is this avicennite?
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 avicennite with a known reference. Avicennite sits at Mohs 1.5-2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: grayish black, black with a brownish tint.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: grayish black.
- 5Look at form & habitCrystal system: cubic. Typical habit: grains.
Often confused with
Avicennite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Hematite is the harder of the two (Mohs 5-6 vs. 1.5-2.5); streak differs, so Avicennite leaves grayish black, black with a brownish tint, Hematite leaves cherry-red or reddish brown.
How to tell apart: Magnetite is the harder of the two (Mohs 5.5-6.5 vs. 1.5-2.5); streak differs, so Avicennite leaves grayish black, black with a brownish tint, Magnetite leaves black.
Often found alongside avicennite
Minerals reported to co-occur with avicennite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Tl₂O₃
- Mohs hardness
- 1.5-2.5
- Density
- 8.9 g/cm³
- Colors
- Streak
- Grayish black, black with a brownish tint
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Cubic
- Crystal habit
- Grains
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In the weathered zone of a hematite-calcite vein cutting banded marmorized and silicified limestones near a granite-gneiss contact (near Dzhuzumli, Tajikistan)
Where rockhounds find avicennite
Classic worldwide localities
- Carlin mine, 50 km northwest of Elko, Lynn district, Eureka Co., Nevada, and near Lookout Pass, Tooele Co., Utah, USA
- Village of Dzhuzumli, Mt. Zirabulaksk region, Samarkand district, western Uzbekistan
Field-hunting tip
Where it forms: In the weathered zone of a hematite-calcite vein cutting banded marmorized and silicified limestones near a granite-gneiss contact (near Dzhuzumli, Tajikistan). If you start seeing hematite, limonite, ferruginous clay minerals in float, you are in the right ground. Typical habit: grains. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify avicennite?+
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Is avicennite safe to handle?+
What rocks look like avicennite?+
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Find avicennite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
