Lorándite is a rare thallium-arsenic sulfosalt that forms striking, dark red crystals. It is best known for being the mineral used in solar neutrino experiments and is typically found in low-temperature hydrothermal veins associated with other arsenic sulfides.
Is this lorándite?
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 lorándite with a known reference. Lorándite sits at Mohs 2-2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: cherry-red.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic, adamantine.
- 4Match the color rangeCompare against the expected color range: red, carmine red, blackish lead gray.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic, tabular.
Often confused with
Lorándite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Lorándite leaves cherry-red, Realgar leaves red-orange to red; luster reads metallic, adamantine on Lorándite and resinous to greasy on Realgar.
How to tell apart: Streak differs, so Lorándite leaves cherry-red, Proustite leaves vermilion; luster reads metallic, adamantine on Lorándite and adamantine on Proustite.
Often found alongside lorándite
Minerals reported to co-occur with lorándite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- TlAsS₂
- Mohs hardness
- 2-2.5
- Density
- 5.53 g/cm³
- Colors
- Streak
- Cherry-red
- Luster
- Metallic, adamantine
- Transparency
- Translucent to transparent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic, tabular
- Cleavage
- Excellent on {100}, very good on {201}, good on {001}
- Rarity
- Rare
- Uses
- Collector, Research
- Host rock
- Although rare, the most widespread thallium mineral; of hydrothermal origin, typically formed at relatively low temperatures
Where rockhounds find lorándite
1 mapped spotsClassic worldwide localities
- New Rambler Cu–Ni mine, Medicine Bow Mountains, east of Encampment, Albany Co., Wyoming, USA
- Carlin mine, 50 km northwest of Elko, Lynn district, Eureka Co., in the Jerritt Canyon mines, Independence Mountains district, Elko Co., and from the Getchell mine, Potosi district, Humboldt Co., Nevada, USA
- Mercur gold deposit, Tooele Co., Utah, USA
- Alšar (Allchar), near Rošden, Macedonia (type locality)
- Dzhizhikrut Sb–Hg deposit, Tajikistan
- Beshtau uranium deposit, near Pyatigorsk, northern Caucasus Mountains, Russia
Field-hunting tip
Where it forms: Although rare, the most widespread thallium mineral; of hydrothermal origin, typically formed at relatively low temperatures. If you start seeing stibnite, realgar, orpiment in float, you are in the right ground. Typical habit: prismatic, tabular. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Wyoming. Start trip planning there.
Common questions
How do you identify lorándite?+
Where is lorándite found?+
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Is lorándite safe to handle?+
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Find lorándite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
