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

mineralrarenull family

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 — Grumiplucite leaves gray, Tiemannite leaves black.

How to tell apart: Streak differs — 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 — that is 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.