Ruarsite is a rare ruthenium-arsenic-sulfur mineral that typically occurs as microscopic inclusions within platinum-group ore deposits. Because it is rarely found in large visible crystals, collectors usually seek out polished ore sections or matrix samples containing associated platinum-group minerals.
Is this ruarsite?
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 ruarsite with a known reference. Ruarsite sits at Mohs 6-7, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: grayish black.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: gray, dark lead gray.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: irregular grains.
Often confused with
Ruarsite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Ruarsite leaves grayish black, Arsenopyrite leaves black.
How to tell apart: Streak differs, so Ruarsite leaves grayish black, Laurite leaves dark gray.
How to tell apart: Streak differs, so Ruarsite leaves grayish black, Sperrylite leaves black.
Often found alongside ruarsite
Minerals reported to co-occur with ruarsite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- RuAsS
- Mohs hardness
- 6-7
- Density
- 7.08 g/cm³
- Colors
- GrayDark lead gray
- Streak
- Grayish black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Irregular grains
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In heavy mineral concentrates and in chromium ore derived from an Alpine-type ultramafic (Anduo, Tibet, China)
Where rockhounds find ruarsite
Classic worldwide localities
- Anduo chromite deposit, northern Tibet, China (type locality)
- Neozhidannyy Creek placers, Tuva, Russia
- Kapitanov chromite deposit, near Zvenyhorodka, Ukraine
- Kraubath ultramafic massif, Styria, Austria
- Kelly Lake Ni–Cu sulfide deposit, Sudbury, Ontario, Canada
Field-hunting tip
Where it forms: In heavy mineral concentrates and in chromium ore derived from an Alpine-type ultramafic (Anduo, Tibet, China). If you start seeing iridosmine, rutheniridosmine, ruthenosmiridium in float, you are in the right ground. Typical habit: irregular grains. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify ruarsite?+
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Find ruarsite on the map
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