Selenopolybasite is a rare selenium-dominant member of the polybasite group, typically found in low-temperature silver-rich hydrothermal veins. It usually appears as dark, metallic, pseudo-hexagonal tabular crystals that are difficult to distinguish visually from other members of the polybasite-pearceite series without laboratory analysis.

Hardness

3-3.5

Mohs

Luster

Metallic

Streak

Black

Transparency

Opaque

mineralrarePolybasite Group family

Selenopolybasite

Hardness: 3-3.5
Luster: Metallic
Streak: Black
Transparency: Opaque

No image

Is this selenopolybasite?

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 selenopolybasite with a known reference. Selenopolybasite sits at Mohs 3-3.5, 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: black.
5
Look at form & habit
Crystal system: trigonal. Typical habit: anhedral grains, microscopic crystals.

Often confused with

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

How to tell apart: Streak differs, so Selenopolybasite leaves black, Stephanite leaves iron-black.

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Often found alongside selenopolybasite

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

All properties

Chemical formula: Cu(Ag,Cu)₆Ag₉Sb₂(S,Se)₉Se₂
Mohs hardness: 3-3.5
Density: 6.548 g/cm³
Colors: Black
Streak: Black
Luster: Metallic
Transparency: Opaque
Crystal system: Trigonal
Crystal habit: Anhedral grains, microscopic crystals
Cleavage: None detected
Rarity: Rare
Uses: Collector
Host rock: In silicious veins through rhyolite porphyry altered at shallow depth by heated brines

Where rockhounds find selenopolybasite

Classic worldwide localities

De Lamar mine, Owyhee County, Idaho, U.S.A (type locality)

Field-hunting tip

Where it forms: In silicious veins through rhyolite porphyry altered at shallow depth by heated brines. If you start seeing naumannite, covellite, pyrite in float, you are in the right ground. Typical habit: anhedral grains, microscopic crystals. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify selenopolybasite?+

Mohs hardness is 3-3.5. Luster: metallic. The streak is black. Common colors include black.

Where is selenopolybasite found?+

Notable localities include De Lamar mine, Owyhee County, Idaho, U.S.A (type locality).

Is selenopolybasite safe to handle?+

Selenopolybasite contains antimony, copper and selenium. Contains silver, copper, antimony, and selenium; avoid inhaling dust or ingesting particles and wash hands thoroughly after handling.

What rocks look like selenopolybasite?+

Selenopolybasite is most often confused with Polybasite, Pearceite, Stephanite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with selenopolybasite?+

Selenopolybasite commonly co-occurs with Naumannite, Covellite, Pyrite, Calcite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does selenopolybasite form in?+

Where it forms: In silicious veins through rhyolite porphyry altered at shallow depth by heated brines. Working float back to the host body is the standard way to chase a fresh occurrence.

What is selenopolybasite used for?+

Selenopolybasite is used in collector.

Find selenopolybasite on the map

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