Ruthenarsenite is a rare ruthenium arsenide mineral typically found as small, metallic grains within platinum group mineral deposits. Collectors usually find it alongside other rare palladium and platinum minerals in specific geological settings like the Stillwater Complex. Due to its rarity, it is almost exclusively a specimen of interest for advanced mineralogists.

Hardness

5-6

Mohs

Luster

Metallic

Streak

Black

Transparency

Opaque

mineralrare

Ruthenarsenite

Hardness: 5-6
Luster: Metallic
Streak: Black
Transparency: Opaque

No image

Is this ruthenarsenite?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch ruthenarsenite with a known reference. Ruthenarsenite sits at Mohs 5-6 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Ruthenarsenite leaves a black streak.
3
Read the luster
Hold the specimen under a strong light. Ruthenarsenite typically shows a metallic luster.
4
Match the color range
Compare against the expected color range: white, silver-white.
5
Look at form & habit
Crystal system: hexagonal. Typical habit: anhedral grains, massive.

Often confused with

Ruthenarsenite vs. its common look-alikes — and how to tell them apart in the field.

Often found alongside ruthenarsenite

Minerals reported to co-occur with ruthenarsenite. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: RuAs
Mohs hardness: 5-6
Density: 9.4-9.6 g/cm³
Colors: White Silver-white
Streak: Black
Luster: Metallic
Transparency: Opaque
Crystal system: Hexagonal
Crystal habit: Anhedral Grains, Massive
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Ultramafic Igneous Complexes, Hydrothermal Veins
Typical price: $50-300 per specimen

Where rockhounds find ruthenarsenite

Classic worldwide localities

Musonoi mine, Democratic Republic of the Congo
Stillwater complex, Montana, USA

Field-hunting tip

Look in ultramafic igneous complexes, hydrothermal veins country — that is the host setting where ruthenarsenite typically forms. If you start seeing sperrylite, platinum group minerals, galena in float, you are in the right ground. Field specimens usually show a anhedral grains, massive habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify ruthenarsenite?+

Mohs hardness is 5-6. It typically shows a metallic luster. The streak is black. Common colors include white, silver-white.

Where is ruthenarsenite found?+

Notable localities include Musonoi mine, Democratic Republic of the Congo; Stillwater complex, Montana, USA.

How much is ruthenarsenite worth?+

Typical asking prices fall in the range of $50-300 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

Is ruthenarsenite safe to handle?+

It contains toxic constituents. Contains arsenic, which is toxic; wash hands after handling and avoid inhaling dust or powder. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like ruthenarsenite?+

Ruthenarsenite is most often confused with Sperrylite, Arsenopyrite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with ruthenarsenite?+

Ruthenarsenite commonly co-occurs with Sperrylite, Platinum group minerals, Galena. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does ruthenarsenite form in?+

Ruthenarsenite typically forms in ultramafic igneous complexes, hydrothermal veins. Working float back to the host body is the standard way to chase a fresh occurrence.

What is ruthenarsenite used for?+

Ruthenarsenite is used in collector.

Find ruthenarsenite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.