Acanthite is the low-temperature stable form of silver sulfide and is the most important silver ore mineral. It often appears as dark, sectile masses or in distinctive pseudocubic crystals after argentite, which is unstable above 173°C.

Hardness

2-2.5

Mohs

Luster

Metallic

Streak

Black

Transparency

Opaque

mineralcommon

Acanthite

Also: Argentite

Hardness: 2-2.5
Luster: Metallic
Streak: Black
Transparency: Opaque

Is this acanthite?

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 acanthite with a known reference. Acanthite sits at Mohs 2-2.5 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Acanthite leaves a black streak.
3
Read the luster
Hold the specimen under a strong light. Acanthite typically shows a metallic luster.
4
Match the color range
Compare against the expected color range: lead-gray, black.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: pseudocubic, massive, reticulated, acicular.

Often confused with

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

mineral

Galena

Mohs 2.5

How to tell apart: Streak differs — Acanthite leaves black, Galena leaves lead-gray.

How to tell apart: Streak differs — Acanthite leaves black, Chalcocite leaves lead-gray to black.

Often found alongside acanthite

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

All properties

Chemical formula: Ag₂S
Mohs hardness: 2-2.5
Density: 7.2-7.4 g/cm³
Colors: Lead-gray Black
Streak: Black
Luster: Metallic
Transparency: Opaque
Crystal system: Monoclinic
Crystal habit: Pseudocubic, Massive, Reticulated, Acicular
Cleavage: None
Rarity: Common
Uses: Collector, Ore
Host rock: Hydrothermal Veins
Typical price: $10-150 thumbnail, $200-800 cabinet

Where rockhounds find acanthite

Classic worldwide localities

Guanajuato, Mexico
Freiberg, Germany
Jáchymov, Czech Republic
Cobalt, Ontario, Canada
Kongsberg, Norway

Field-hunting tip

Look in hydrothermal veins country — that is the host setting where acanthite typically forms. If you start seeing silver, galena, sphalerite in float, you are in the right ground. Field specimens usually show a pseudocubic, massive, reticulated, acicular habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify acanthite?+

Mohs hardness is 2-2.5. It typically shows a metallic luster. The streak is black. Common colors include lead-gray, black.

Where is acanthite found?+

Notable localities include Guanajuato, Mexico; Freiberg, Germany; Jáchymov, Czech Republic; Cobalt, Ontario, Canada; Kongsberg, Norway.

How much is acanthite worth?+

Typical asking prices fall in the range of $10-150 thumbnail, $200-800 cabinet. Quality, size, and provenance can move individual specimens well outside that range.

Is acanthite safe to handle?+

It contains toxic constituents. Acanthite contains silver and sulfur; it is stable but can release trace amounts of sulfides; handle with care and wash hands after contact as it contains potentially toxic elements. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like acanthite?+

Acanthite is most often confused with Galena, Chalcocite, Argentite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with acanthite?+

Acanthite commonly co-occurs with Silver, Galena, Sphalerite, Chalcopyrite, Calcite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does acanthite form in?+

Acanthite typically forms in hydrothermal veins. Working float back to the host body is the standard way to chase a fresh occurrence.

What is acanthite used for?+

Acanthite is used in collector, ore.

Find acanthite on the map

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