Drysdallite is a rare molybdenum selenide mineral that looks very similar to molybdenite but typically occurs in distinct selenium-rich environments. It is characterized by its soft, flexible, and sectile nature, often forming platy or foliated aggregates that can be easily mistaken for graphite or molybdenite without chemical analysis.

Hardness

1-1.5

Mohs

Luster

Metallic

Streak

Brownish black

Transparency

Opaque

mineralrareMolybdenite Group family

Drysdallite

Hardness: 1-1.5
Luster: Metallic
Streak: Brownish black
Transparency: Opaque

Is this drysdallite?

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 drysdallite with a known reference. Drysdallite sits at Mohs 1-1.5, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: brownish 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: hexagonal. Typical habit: foliated, platy, lamellar aggregates.

Often confused with

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

mineral

Molybdenite

Mohs 1-1.5

How to tell apart: Streak differs, so Drysdallite leaves brownish black, Molybdenite leaves bluish gray.

How to tell apart: Streak differs, so Drysdallite leaves brownish black, Graphite leaves black to steel-gray, shining.

Compare →

Often found alongside drysdallite

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

All properties

Chemical formula: MoSe₂
Mohs hardness: 1-1.5
Density: 6.25 g/cm³
Colors: Grayish black
Streak: Brownish black
Luster: Metallic
Transparency: Opaque
Crystal system: Hexagonal
Crystal habit: Foliated, platy, lamellar aggregates
Cleavage: {0001}, perfect
Rarity: Rare
Uses: Collector
Host rock: In the oxidation zone of a uranium deposit in a talc schist

Where rockhounds find drysdallite

Classic worldwide localities

Kapijimpanga uranium deposit, 16 km southeast of Solwezi, Northwestern Province, Zambia (type locality)

Field-hunting tip

Where it forms: In the oxidation zone of a uranium deposit in a talc schist. If you start seeing uraninite, apatite, masuyite in float, you are in the right ground. Typical habit: foliated, platy, lamellar aggregates. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify drysdallite?+

Mohs hardness is 1-1.5. Luster: metallic. The streak is brownish black. Common colors include grayish black.

Where is drysdallite found?+

Notable localities include Kapijimpanga uranium deposit, 16 km southeast of Solwezi, Northwestern Province, Zambia (type locality).

Is drysdallite safe to handle?+

Drysdallite contains selenium. Wash your hands afterwards, never grind or breathe the dust, and store it apart from specimens you handle often.

What rocks look like drysdallite?+

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

What minerals are found with drysdallite?+

Drysdallite commonly co-occurs with Uraninite, Apatite, Masuyite, Secondary uranium minerals. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does drysdallite form in?+

Where it forms: In the oxidation zone of a uranium deposit in a talc schist. Working float back to the host body is the standard way to chase a fresh occurrence.

What is drysdallite used for?+

Drysdallite is used in collector.

Find drysdallite on the map

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