Gruzdevite is a rare mercury-copper sulfosalt known primarily from the Khaydarkan deposit in Kyrgyzstan. It typically occurs as microscopic, gray-black metallic grains embedded within other sulfide minerals, making it a challenging species for field identification without analytical methods.

Hardness

4.5

Mohs

Luster

Metallic

Streak

Black

Transparency

Opaque

mineralrare

Gruzdevite

Hardness: 4.5
Luster: Metallic
Streak: Black
Transparency: Opaque

No image

Is this gruzdevite?

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 gruzdevite with a known reference. Gruzdevite sits at Mohs 4.5, 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: grayish black.
5
Look at form & habit
Crystal system: trigonal. Typical habit: anhedral grains.

Often confused with

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

How to tell apart: Streak differs, so Gruzdevite leaves black, Tennantite leaves reddish gray.

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Often found alongside gruzdevite

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

All properties

Chemical formula: Cu₆Hg₃Sb₄S₁₂
Mohs hardness: 4.5
Density: 5.88 g/cm³
Colors: Grayish black
Streak: Black
Luster: Metallic
Transparency: Opaque
Crystal system: Trigonal
Crystal habit: Anhedral grains
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: In veinlets of probable low-temperature hydrothermal origin (Chauvai deposit, Kyrgyzstan)

Where rockhounds find gruzdevite

Classic worldwide localities

Goldstrike mine, Lynn district, Eureka Co., Nevada, USA
Chauvai Sb–Hg deposit, Fergana Valley, Alai Range, southern Kyrgyzstan (type locality)
San Miguel prospect, 10 km northwest of the Moctezuma (Bambolla) mine, 12 km south of Moctezuma, Sonora, Mexico

Field-hunting tip

Where it forms: In veinlets of probable low-temperature hydrothermal origin (Chauvai deposit, Kyrgyzstan). If you start seeing aktashite, stibnite, cinnabar in float, you are in the right ground. Typical habit: anhedral grains. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify gruzdevite?+

Mohs hardness is 4.5. Luster: metallic. The streak is black. Common colors include grayish black.

Where is gruzdevite found?+

Notable localities include Goldstrike mine, Lynn district, Eureka Co., Nevada, USA; Chauvai Sb–Hg deposit, Fergana Valley, Alai Range, southern Kyrgyzstan (type locality); San Miguel prospect, 10 km northwest of the Moctezuma (Bambolla) mine, 12 km south of Moctezuma, Sonora, Mexico.

Is gruzdevite safe to handle?+

Gruzdevite contains antimony, copper and mercury and calls for real care. Contains mercury and antimony; avoid creating dust, wash hands thoroughly after handling, and store in a sealed container.

What rocks look like gruzdevite?+

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

What minerals are found with gruzdevite?+

Gruzdevite commonly co-occurs with Aktashite, Stibnite, Cinnabar, Metacinnabar, Wurtzite, Fluorite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does gruzdevite form in?+

Where it forms: In veinlets of probable low-temperature hydrothermal origin (Chauvai deposit, Kyrgyzstan). Working float back to the host body is the standard way to chase a fresh occurrence.

What is gruzdevite used for?+

Gruzdevite is used in collector.

Find gruzdevite on the map

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