Dalnegroite is an extremely rare thallium-lead sulfosalt discovered in the skarn deposits of the Primorskiy Kray region in Russia. It typically occurs as small, lead-gray grains within complex sulfide-rich assemblages and is highly prized by advanced mineralogists for its unique composition.
Is this dalnegroite?
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 dalnegroite with a known reference. Dalnegroite sits at Mohs 3-3.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Dalnegroite leaves a brownish-red streak.
- 3Read the lusterHold the specimen under a strong light. Dalnegroite typically shows a submetallic luster.
- 4Match the color rangeCompare against the expected color range: lead-gray, dark gray.
- 5Look at form & habitCrystal system: triclinic. Typical habit: granular to massive.
Often confused with
Dalnegroite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Dalnegroite leaves brownish-red, Galena leaves lead-gray; luster reads submetallic on Dalnegroite and metallic on Galena.
How to tell apart: Streak differs, so Dalnegroite leaves brownish-red, Bournonite leaves steel-gray; luster reads submetallic on Dalnegroite and dull on Bournonite.
How to tell apart: Streak differs, so Dalnegroite leaves brownish-red, Sartorite leaves chocolate-brown; luster reads submetallic on Dalnegroite and metallic on Sartorite.
Often found alongside dalnegroite
Minerals reported to co-occur with dalnegroite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Tl,Pb)₃AsS₃
- Mohs hardness
- 3-3.5
- Density
- 4.82 g/cm³
- Streak
- Brownish-red
- Luster
- Submetallic
- Transparency
- Opaque
- Crystal system
- Triclinic
- Crystal habit
- Granular to Massive
- Cleavage
- None Discernable
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Skarn Deposits
Where rockhounds find dalnegroite
Classic worldwide localities
- Lengenbach quarry, Binntal, Switzerland
Field-hunting tip
Look in skarn deposits country, the host setting where dalnegroite typically forms. If you start seeing galena, sphalerite, pyrite in float, you are in the right ground. Field specimens usually show a granular to massive habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find dalnegroite on the map
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