Tristramite is a rare phosphate mineral characterized by its uranium content and earthy, often inconspicuous habit. It is typically found in the alteration zones of hydrothermal uranium deposits, often as coatings or fracture fillings.

Hardness

3.5-4

Mohs

Luster

Dull

Streak

White

Transparency

Opaque

mineralrareRhabdophane Group family

Tristramite

Hardness: 3.5-4
Luster: Dull
Streak: White
Transparency: Opaque

Is this tristramite?

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 tristramite with a known reference. Tristramite 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. Tristramite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Tristramite typically shows a dull luster.
4
Match the color range
Compare against the expected color range: white, yellowish, brown.
5
Look at form & habit
Crystal system: trigonal. Typical habit: microcrystalline aggregates, earthy.

Often found alongside tristramite

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

All properties

Chemical formula: (Ca,U,Fe)(PO₄,SO₄)·2H₂O
Mohs hardness: 3.5-4
Density: 4.8 g/cm³
Colors: White Yellowish Brown
Streak: White
Luster: Dull
Transparency: Opaque
Crystal system: Trigonal
Crystal habit: Microcrystalline Aggregates, Earthy
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Hydrothermal Uranium Veins
Typical price: $50-300 per specimen

Where rockhounds find tristramite

Classic worldwide localities

Tristramite locality, Cornwall, UK
various uranium mines in France
Czech Republic

Field-hunting tip

Look in hydrothermal uranium veins country — that is the host setting where tristramite typically forms. If you start seeing uraninite, fluorite, quartz in float, you are in the right ground. Field specimens usually show a microcrystalline aggregates, earthy habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify tristramite?+

Mohs hardness is 3.5-4. It typically shows a dull luster. The streak is white. Common colors include white, yellowish, brown.

Where is tristramite found?+

Notable localities include Tristramite locality, Cornwall, UK; various uranium mines in France; Czech Republic.

How much is tristramite worth?+

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

Is tristramite safe to handle?+

This mineral is radioactive. Contains uranium; handle with care, avoid inhaling dust, and wash hands thoroughly after contact. Handle with care, avoid grinding or breathing dust, and store separately.

What minerals are found with tristramite?+

Tristramite commonly co-occurs with Uraninite, Fluorite, Quartz, Hematite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does tristramite form in?+

Tristramite typically forms in hydrothermal uranium veins. Working float back to the host body is the standard way to chase a fresh occurrence.

What is tristramite used for?+

Tristramite is used in collector.

Find tristramite on the map

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