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

3-4

Mohs

Luster

Vitreous

Streak

White

Transparency

Semitransparent

mineralrareRhabdophane Group family

Tristramite

Hardness: 3-4
Luster: Vitreous
Streak: White
Transparency: Semitransparent

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 3-4, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: white.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
4
Match the color range
Compare against the expected color range: green yellow, light yellow.
5
Look at form & habit
Crystal system: hexagonal. 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: 3-4
Density: 3.8-4.2 g/cm³
Colors: Green yellow Light yellow
Streak: White
Luster: Vitreous
Transparency: Semitransparent
Crystal system: Hexagonal
Crystal habit: Microcrystalline aggregates, earthy
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: In fractures and cavities in hydrothermal veins

Where rockhounds find tristramite

Classic worldwide localities

Cornwall, at Wheal Trewavas, Breage, England
Trequeen, England
Wheal Buller, Redruth, England
Wheal Damsel, Gwennap, England
Wheals Providence and Alice, Lelant, England

Field-hunting tip

Where it forms: In fractures and cavities in hydrothermal veins. If you start seeing uraninite, goethite, digenite in float, you are in the right ground. Typical habit: microcrystalline aggregates, earthy. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify tristramite?+

Mohs hardness is 3-4. Luster: vitreous. The streak is white. Common colors include green yellow, light yellow.

Where is tristramite found?+

Notable localities include Cornwall, at Wheal Trewavas, Breage, England; Trequeen, England; Wheal Buller, Redruth, England; Wheal Damsel, Gwennap, England; Wheals Providence and Alice, Lelant, England.

Is tristramite safe to handle?+

Tristramite contains uranium or thorium and calls for real care. Contains uranium; handle with care, avoid inhaling dust, and wash hands thoroughly after contact.

What minerals are found with tristramite?+

Tristramite commonly co-occurs with Uraninite, Goethite, Digenite, Chalcopyrite, Pyrite, Sphalerite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does tristramite form in?+

Where it forms: In fractures and cavities in hydrothermal 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.