Cuboargyrite is a rare high-temperature polymorph of silver sulfide that typically occurs as cubic crystals. It is chemically identical to acanthite but crystallizes in the isometric system, often appearing as an inversion product. Collectors usually find it as small, metallic-gray crystals within complex silver-bearing hydrothermal vein systems.

Hardness

2.5

Mohs

Luster

Metallic

Streak

Black

Transparency

Opaque

mineralrareAcanthite Group family

Cuboargyrite

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

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Is this cuboargyrite?

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 cuboargyrite with a known reference. Cuboargyrite sits at Mohs 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. Cuboargyrite leaves a black streak.
3
Read the luster
Hold the specimen under a strong light. Cuboargyrite 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: cubic. Typical habit: pseudocubic crystals.

Often confused with

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

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

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Often found alongside cuboargyrite

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

All properties

Chemical formula: Ag₂S
Mohs hardness: 2.5
Density: 7.3 g/cm³
Colors: Lead-gray Black
Streak: Black
Luster: Metallic
Transparency: Opaque
Crystal system: Cubic
Crystal habit: Pseudocubic Crystals
Cleavage: None
Rarity: Rare
Uses: Collector, Scientific Research
Host rock: Hydrothermal Veins
Typical price: $50-500 depending on specimen quality and rarity

Where rockhounds find cuboargyrite

Classic worldwide localities

Schneeberg, Germany
Jáchymov, Czech Republic
Guanajuato, Mexico

Field-hunting tip

Look in hydrothermal veins country — that is the host setting where cuboargyrite typically forms. If you start seeing native silver, proustite, pyrargyrite in float, you are in the right ground. Field specimens usually show a pseudocubic crystals habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify cuboargyrite?+

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

Where is cuboargyrite found?+

Notable localities include Schneeberg, Germany; Jáchymov, Czech Republic; Guanajuato, Mexico.

How much is cuboargyrite worth?+

Typical asking prices fall in the range of $50-500 depending on specimen quality and rarity. Quality, size, and provenance can move individual specimens well outside that range.

Is cuboargyrite safe to handle?+

It contains toxic constituents. Contains silver and sulfur; wash hands after handling and avoid inhaling dust. Generally associated with other toxic heavy metal sulfides. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like cuboargyrite?+

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

What minerals are found with cuboargyrite?+

Cuboargyrite commonly co-occurs with Native Silver, Proustite, Pyrargyrite, Galena. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does cuboargyrite form in?+

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

What is cuboargyrite used for?+

Cuboargyrite is used in collector, scientific research.

Find cuboargyrite on the map

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