Grumiplucite is an extremely rare mercury bismuth selenide mineral first described from the Grumipluca mine in Italy. It typically occurs as microscopic inclusions within other sulfide minerals, making it a challenging and prized specimen for micromounters. Collectors should handle it with caution due to its mercury content.

Hardness

1.5-2

Mohs

Luster

Metallic

Streak

Gray

Transparency

Opaque

mineralrare

Grumiplucite

Hardness: 1.5-2
Luster: Metallic
Streak: Gray
Transparency: Opaque

Is this grumiplucite?

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 grumiplucite with a known reference. Grumiplucite sits at Mohs 1.5-2, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Grumiplucite leaves a gray streak.
3
Read the luster
Hold the specimen under a strong light. Grumiplucite typically shows a metallic luster.
4
Match the color range
Compare against the expected color range: gray, white.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: microscopic grains.

Often confused with

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

mineral

Tiemannite

Mohs 2.5

How to tell apart: Streak differs, so Grumiplucite leaves gray, Tiemannite leaves black.

How to tell apart: Streak differs, so Grumiplucite leaves gray, Clausthalite leaves gray-black.

Compare →

Often found alongside grumiplucite

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

All properties

Chemical formula: HgBi₂Se₄
Mohs hardness: 1.5-2
Density: 8.5 g/cm³
Colors: Gray White
Streak: Gray
Luster: Metallic
Transparency: Opaque
Crystal system: Monoclinic
Crystal habit: Microscopic Grains
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Hydrothermal Veins
Typical price: expensive due to rarity

Where rockhounds find grumiplucite

Classic worldwide localities

Grumipluca, Italy

Field-hunting tip

Look in hydrothermal veins country, the host setting where grumiplucite typically forms. If you start seeing cinnabar, pyrite, calcite in float, you are in the right ground. Field specimens usually show a microscopic grains habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify grumiplucite?+

Mohs hardness is 1.5-2. It typically shows a metallic luster. The streak is gray. Common colors include gray, white.

Where is grumiplucite found?+

Notable localities include Grumipluca, Italy.

How much is grumiplucite worth?+

Typical asking prices fall in the range of expensive due to rarity. Quality, size, and provenance can move individual specimens well outside that range.

Is grumiplucite safe to handle?+

It contains toxic constituents. Contains mercury and selenium; wash hands thoroughly after handling and avoid inhaling dust. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like grumiplucite?+

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

What minerals are found with grumiplucite?+

Grumiplucite commonly co-occurs with cinnabar, pyrite, calcite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does grumiplucite form in?+

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

What is grumiplucite used for?+

Grumiplucite is used in collector.

Find grumiplucite on the map

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