Pääkkönenite is a rare antimony arsenic sulfide mineral originally discovered in the Seinäjoki antimony deposits of Finland. It typically forms metallic, gray, acicular crystals or fibrous aggregates that are visually similar to stibnite but distinguishable by its distinct composition and crystal system.

Hardness

Mohs

Luster

Metallic

Streak

Gray with a brownish tint

Transparency

Opaque

mineralrare

Pääkkönenite

Hardness: ~2
Luster: Metallic
Streak: Gray with a brownish tint
Transparency: Opaque

Is this pääkkönenite?

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 pääkkönenite with a known reference. Pääkkönenite sits at Mohs ~2, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: gray with a brownish tint.
3
Read the luster
Hold the specimen under a strong light. Luster: metallic.
4
Match the color range
Compare against the expected color range: gray.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: irregular grains.

Often confused with

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

mineral

Stibnite

Mohs 2

How to tell apart: Streak differs, so Pääkkönenite leaves gray with a brownish tint, Stibnite leaves lead-gray.

How to tell apart: Arsenopyrite is the harder of the two (Mohs 5.5-6 vs. ~2); streak differs, so Pääkkönenite leaves gray with a brownish tint, Arsenopyrite leaves black.

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Often found alongside pääkkönenite

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

All properties

Chemical formula: Sb₂AsS₂
Mohs hardness: ~2
Density: 5.21 g/cm³
Colors: Gray
Streak: Gray with a brownish tint
Luster: Metallic
Transparency: Opaque
Crystal system: Monoclinic
Crystal habit: Irregular grains
Cleavage: In one direction
Rarity: Rare
Uses: Collector
Host rock: In hydrothermal mineral deposits with other Sb–As-bearing minerals

Where rockhounds find pääkkönenite

Classic worldwide localities

Kalliosalo deposit, Seinäjoki region, Finland (type locality)
Příbram, Czech Republic
Hemlo gold deposit, Hemlo, Ontario, Canada

Field-hunting tip

Where it forms: In hydrothermal mineral deposits with other Sb–As-bearing minerals. If you start seeing arsenopyrite, arsenic, löllingite 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 pääkkönenite?+

Mohs hardness is ~2. Luster: metallic. The streak is gray with a brownish tint. Common colors include gray.

Where is pääkkönenite found?+

Notable localities include Kalliosalo deposit, Seinäjoki region, Finland (type locality); Příbram, Czech Republic; Hemlo gold deposit, Hemlo, Ontario, Canada.

Is pääkkönenite safe to handle?+

Pääkkönenite contains antimony and arsenic and calls for real care. Contains arsenic and antimony. Wash hands thoroughly after handling specimens and avoid inhaling dust when cleaning or trimming.

What rocks look like pääkkönenite?+

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

What minerals are found with pääkkönenite?+

Pääkkönenite commonly co-occurs with Arsenopyrite, Arsenic, Löllingite, Stibnite, Antimony, Stibarsen. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does pääkkönenite form in?+

Where it forms: In hydrothermal mineral deposits with other Sb–As-bearing minerals. Working float back to the host body is the standard way to chase a fresh occurrence.

What is pääkkönenite used for?+

Pääkkönenite is used in collector.

Find pääkkönenite on the map

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