Törnroosite is a rare palladium arsenic telluride that forms black irregular subrounded grains. It was approved as a distinct mineral species in 2010. It was first described from Miessijoki River, Lemmenjoki area, Inari Commune, Finnish Lapland, Finland.
Is this törnroosite?
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 törnroosite with a known reference. Törnroosite sits at Mohs 5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Törnroosite leaves a silvery black streak.
- 3Read the lusterHold the specimen under a strong light. Törnroosite typically shows a metallic luster.
- 4Match the color rangeCompare against the expected color range: black.
- 5Look at form & habitCrystal system: cubic. Typical habit: irregular subrounded grains.
Often confused with
Törnroosite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Sperrylite is the harder of the two (Mohs 6-7 vs. 5); streak differs, so Törnroosite leaves silvery black, Sperrylite leaves black.
How to tell apart: Streak differs, so Törnroosite leaves silvery black, Cooperite leaves black.
Often found alongside törnroosite
Minerals reported to co-occur with törnroosite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Pd₁₁As₂Te₂
- Mohs hardness
- 5
- Density
- 11.205 g/cm³
- Colors
- Streak
- Silvery Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Cubic
- Crystal habit
- Irregular Subrounded Grains
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Copper-nickel Sulfide Deposits
Where rockhounds find törnroosite
Classic worldwide localities
- Miessijoki River, Finnish Lapland, Finland
Field-hunting tip
Look in copper-nickel sulfide deposits country, the host setting where törnroosite typically forms. If you start seeing sperrylite, platinum, chalcopyrite in float, you are in the right ground. Field specimens usually show a irregular subrounded grains habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find törnroosite on the map
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