Cliffordite is a rare uranium tellurite mineral typically found as small, brilliant yellow octahedral crystals in oxidized ore zones. Because of its radioactive and toxic nature, it is highly sought after by advanced mineral collectors specializing in tellurium species.

Hardness

3.5

Mohs

Luster

Adamantine

Streak

White

Transparency

Transparent

mineralrare

Cliffordite

Hardness: 3.5
Luster: Adamantine
Streak: White
Transparency: Transparent

Is this cliffordite?

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 cliffordite with a known reference. Cliffordite sits at Mohs 3.5 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Cliffordite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Cliffordite typically shows a adamantine luster.
4
Match the color range
Compare against the expected color range: yellow, yellowish-green, colorless.
5
Look at form & habit
Crystal system: cubic. Typical habit: octahedral crystals, often with rounded faces or striations.

Often confused with

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

mineral

Empressite

Mohs 3.5

How to tell apart: Streak differs — Cliffordite leaves white, Empressite leaves black; luster reads adamantine on Cliffordite and metallic on Empressite.

How to tell apart: Cliffordite is noticeably harder (Mohs 3.5 vs. 2).

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Often found alongside cliffordite

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

All properties

Chemical formula: UTe₃O₉
Mohs hardness: 3.5
Density: 6.32 g/cm³
Colors: Yellow Yellowish-green Colorless
Streak: White
Luster: Adamantine
Transparency: Transparent
Crystal system: Cubic
Crystal habit: Octahedral Crystals, Often with Rounded Faces or Striations
Cleavage: None
Rarity: Rare
Uses: Collector, Scientific Research
Host rock: Oxidized Hydrothermal Tellurium-bearing Deposits
Typical price: $50-300+ for small specimens

Where rockhounds find cliffordite

Classic worldwide localities

Moab, Utah, USA
Tombstone, Arizona, USA
Old Cabin mine, Colorado, USA

Field-hunting tip

Look in oxidized hydrothermal tellurium-bearing deposits country — that is the host setting where cliffordite typically forms. If you start seeing emmonsite, quetzalcoatlite, tellurite in float, you are in the right ground. Field specimens usually show a octahedral crystals, often with rounded faces or striations habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify cliffordite?+

Mohs hardness is 3.5. It typically shows a adamantine luster. The streak is white. Common colors include yellow, yellowish-green, colorless.

Where is cliffordite found?+

Notable localities include Moab, Utah, USA; Tombstone, Arizona, USA; Old Cabin mine, Colorado, USA.

How much is cliffordite worth?+

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

Is cliffordite safe to handle?+

This mineral is radioactive. It contains toxic constituents. This mineral contains uranium and tellurium; it is both radioactive and toxic. Handle with care, wear gloves, and wash hands thoroughly after handling. Store in a shielded container. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like cliffordite?+

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

What minerals are found with cliffordite?+

Cliffordite commonly co-occurs with Emmonsite, Quetzalcoatlite, Tellurite, Quartz. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does cliffordite form in?+

Cliffordite typically forms in oxidized hydrothermal tellurium-bearing deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is cliffordite used for?+

Cliffordite is used in collector, scientific research.

Find cliffordite on the map

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