Derriksite is an extremely rare secondary copper uranyl selenite mineral typically found as small, vibrant emerald-green platy crystals. It occurs primarily in the oxidation zones of uranium deposits where selenium is present. Due to its scarcity and radioactivity, it is highly sought after by advanced systematic mineral collectors.

Hardness

2-3

Mohs

Luster

Adamantine

Streak

Pale green

Transparency

Semitransparent

mineralrare

Derriksite

Hardness: 2-3
Luster: Adamantine
Streak: Pale green
Transparency: Semitransparent

Is this derriksite?

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 derriksite with a known reference. Derriksite sits at Mohs 2-3, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: pale green.
3
Read the luster
Hold the specimen under a strong light. Luster: adamantine.
4
Match the color range
Compare against the expected color range: bottle green, green.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: platy crystals, crusts, tabular.

Often confused with

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

How to tell apart: Luster reads adamantine on Derriksite and vitreous to subadamantine, pearly on {0001} on Chalcophyllite.

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Often found alongside derriksite

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

All properties

Chemical formula: Cu₄(UO₂)(SeO₃)₂(OH)₆
Mohs hardness: 2-3
Density: 4.72 g/cm³
Colors: Bottle greenGreen
Streak: Pale green
Luster: Adamantine
Transparency: Semitransparent
Crystal system: Orthorhombic
Crystal habit: Platy crystals, crusts, tabular
Cleavage: On {010}, very good
Rarity: Rare
Uses: Collector
Host rock: Very rare in the oxidized portions of a selenium-bearing Cu–Co deposit

Where rockhounds find derriksite

Classic worldwide localities

Musonoi Cu–Co mine, near Kolwezi, Katanga Province, Congo (Shaba Province, Zaire)

Field-hunting tip

Where it forms: Very rare in the oxidized portions of a selenium-bearing Cu–Co deposit. If you start seeing selenian digenite, chalcomenite, demesmaekerite in float, you are in the right ground. Typical habit: platy crystals, crusts, tabular. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify derriksite?+

Mohs hardness is 2-3. Luster: adamantine. The streak is pale green. Common colors include bottle green, green.

Where is derriksite found?+

Notable localities include Musonoi Cu–Co mine, near Kolwezi, Katanga Province, Congo (Shaba Province, Zaire).

Is derriksite safe to handle?+

Derriksite contains copper, uranium or thorium and selenium and calls for real care. Contains uranium and selenium; handle with care. Radioactive, keep stored behind shielding; avoid inhalation of dust or ingestion.

What rocks look like derriksite?+

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

What minerals are found with derriksite?+

Derriksite commonly co-occurs with Selenian digenite, Chalcomenite, Demesmaekerite, Malachite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does derriksite form in?+

Where it forms: Very rare in the oxidized portions of a selenium-bearing Cu–Co deposit. Working float back to the host body is the standard way to chase a fresh occurrence.

What is derriksite used for?+

Derriksite is used in collector.

Find derriksite on the map

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