Arsenopalladinite is an extremely rare palladium arsenide that typically occurs as small, metallic grains within mineralized zones. It is most often identified through micro-analysis in advanced collections due to its scarcity and similarity to other platinum-group minerals.

Hardness

Mohs

Luster

Metallic

Streak

Black

Transparency

Opaque

mineralrare

Arsenopalladinite

Hardness: 4
Luster: Metallic
Streak: Black
Transparency: Opaque

Is this arsenopalladinite?

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 arsenopalladinite with a known reference. Arsenopalladinite sits at Mohs 4, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: black.
3
Read the luster
Hold the specimen under a strong light. Luster: metallic.
4
Match the color range
Compare against the expected color range: silver white.
5
Look at form & habit
Crystal system: triclinic. Typical habit: anhedral grains, nuggets.

Often confused with

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

Often found alongside arsenopalladinite

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

All properties

Chemical formula: Pd₈As₃
Mohs hardness: 4
Density: 10.40 g/cm³
Colors: Silver white
Streak: Black
Luster: Metallic
Transparency: Opaque
Crystal system: Triclinic
Crystal habit: Anhedral grains, nuggets
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: In gold concentrates

Where rockhounds find arsenopalladinite

Classic worldwide localities

Stillwater complex, Montana, USA
Minas Gerais, in the Itabira district (type locality), and at the Caue iron mine, Brazil
Merensky Reef, Bushveldt complex, Transvaal, South Africa
Siikakämä and Konttijarvi intrusions, northern Finland

Field-hunting tip

Where it forms: In gold concentrates. If you start seeing hematite, palladian gold, atheneite in float, you are in the right ground. Typical habit: anhedral grains, nuggets. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify arsenopalladinite?+

Mohs hardness is 4. Luster: metallic. The streak is black. Common colors include silver white.

Where is arsenopalladinite found?+

Notable localities include Stillwater complex, Montana, USA; Minas Gerais, in the Itabira district (type locality), and at the Caue iron mine, Brazil; Merensky Reef, Bushveldt complex, Transvaal, South Africa; Siikakämä and Konttijarvi intrusions, northern Finland.

Is arsenopalladinite safe to handle?+

Arsenopalladinite contains arsenic and calls for real care. Contains arsenic, a toxic element. Handle with care, avoid inhaling dust, and wash hands thoroughly after handling.

What rocks look like arsenopalladinite?+

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

What minerals are found with arsenopalladinite?+

Arsenopalladinite commonly co-occurs with Hematite, Palladian gold, Atheneite, Stillwaterite, Palladseite, Isomertieite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does arsenopalladinite form in?+

Where it forms: In gold concentrates. Working float back to the host body is the standard way to chase a fresh occurrence.

What is arsenopalladinite used for?+

Arsenopalladinite is used in collector.

Find arsenopalladinite on the map

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