Eylettersite is a rare phosphate-sulfate mineral member of the woodhouseite group, primarily known as a secondary mineral in uranium-bearing pegmatites. It typically occurs as minute, crust-like or massive aggregates and is of interest primarily to advanced systematic mineral collectors due to its radioactive nature and scarcity.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent

mineralrareWoodhouseite Group family

Eylettersite

Hardness: 5
Luster: Vitreous
Streak: White
Transparency: Translucent

Is this eylettersite?

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 eylettersite with a known reference. Eylettersite sits at Mohs 5 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Eylettersite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Eylettersite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: white, colorless, yellowish.
5
Look at form & habit
Crystal system: trigonal. Typical habit: microscopic crystals, massive, crusts.

Often confused with

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

Often found alongside eylettersite

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

All properties

Chemical formula: Th(PO₄,SO₄)₂(OH,H₂O)₄
Mohs hardness: 5
Density: 3.31 g/cm³
Colors: White Colorless Yellowish
Streak: White
Luster: Vitreous
Transparency: Translucent
Crystal system: Trigonal
Crystal habit: Microscopic Crystals, Massive, Crusts
Cleavage: None Observed
Rarity: Rare
Uses: Collector
Host rock: Granite Pegmatites
Typical price: $50-300 per specimen

Where rockhounds find eylettersite

Classic worldwide localities

Kobokobo, Democratic Republic of the Congo
Lachaux, France

Field-hunting tip

Look in granite pegmatites country — that is the host setting where eylettersite typically forms. If you start seeing meta-autunite, phosphuranylite, beryl in float, you are in the right ground. Field specimens usually show a microscopic crystals, massive, crusts habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify eylettersite?+

Mohs hardness is 5. It typically shows a vitreous luster. The streak is white. Common colors include white, colorless, yellowish.

Where is eylettersite found?+

Notable localities include Kobokobo, Democratic Republic of the Congo; Lachaux, France.

How much is eylettersite 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 eylettersite safe to handle?+

This mineral is radioactive. Contains thorium, which is radioactive. Handle with care, wash hands after handling, and store in a lead-lined container or away from other specimens. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like eylettersite?+

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

What minerals are found with eylettersite?+

Eylettersite commonly co-occurs with Meta-autunite, Phosphuranylite, Beryl. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does eylettersite form in?+

Eylettersite typically forms in granite pegmatites. Working float back to the host body is the standard way to chase a fresh occurrence.

What is eylettersite used for?+

Eylettersite is used in collector.

Find eylettersite on the map

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