Tyrrellite is a very rare copper-iron-cobalt selenide mineral that typically forms as small, steel-grey metallic grains. It is most famous for its occurrences in selenide-rich hydrothermal mineral assemblages, often found alongside clausthalite.

Hardness

3.5-4

Mohs

Luster

Metallic

Streak

Black

Transparency

Opaque

mineralrareLinnaeite Group family

Tyrrellite

Hardness: 3.5-4
Luster: Metallic
Streak: Black
Transparency: Opaque

Is this tyrrellite?

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 tyrrellite with a known reference. Tyrrellite sits at Mohs 3.5-4 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Tyrrellite leaves a black streak.
3
Read the luster
Hold the specimen under a strong light. Tyrrellite typically shows a metallic luster.
4
Match the color range
Compare against the expected color range: gray, steel gray.
5
Look at form & habit
Crystal system: cubic. Typical habit: granular, massive, anhedral to subhedral crystals.

Often confused with

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

mineral

Clausthalite

Mohs 2.5-3

How to tell apart: Streak differs — Tyrrellite leaves black, Clausthalite leaves gray-black.

How to tell apart: Tyrrellite is noticeably harder (Mohs 3.5-4 vs. 2).

Often found alongside tyrrellite

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

All properties

Chemical formula: (Cu,Fe,Co)₃Se₄
Mohs hardness: 3.5-4
Density: 5.6 g/cm³
Colors: Gray Steel Gray
Streak: Black
Luster: Metallic
Transparency: Opaque
Crystal system: Cubic
Crystal habit: Granular, Massive, Anhedral to Subhedral Crystals
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Hydrothermal Veins, Selenide-bearing Deposits
Typical price: $50-300 for small microspecimens

Where rockhounds find tyrrellite

Classic worldwide localities

Hope's Nose, Torquay, England
Skrikerum, Sweden
Krunkelbach valley, Germany

Field-hunting tip

Look in hydrothermal veins, selenide-bearing deposits country — that is the host setting where tyrrellite typically forms. If you start seeing clausthalite, gold, hematite in float, you are in the right ground. Field specimens usually show a granular, massive, anhedral to subhedral crystals habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify tyrrellite?+

Mohs hardness is 3.5-4. It typically shows a metallic luster. The streak is black. Common colors include gray, steel gray.

Where is tyrrellite found?+

Notable localities include Hope's Nose, Torquay, England; Skrikerum, Sweden; Krunkelbach valley, Germany.

How much is tyrrellite worth?+

Typical asking prices fall in the range of $50-300 for small microspecimens. Quality, size, and provenance can move individual specimens well outside that range.

Is tyrrellite safe to handle?+

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

What rocks look like tyrrellite?+

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

What minerals are found with tyrrellite?+

Tyrrellite commonly co-occurs with Clausthalite, Gold, Hematite, Calcite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does tyrrellite form in?+

Tyrrellite typically forms in hydrothermal veins, selenide-bearing deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is tyrrellite used for?+

Tyrrellite is used in collector.

Find tyrrellite on the map

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