Jáchymovite is a rare secondary uranium sulfate mineral discovered in the historic mines of Jáchymov. It typically occurs as delicate, bright yellow crystalline crusts or aggregates associated with other uranium minerals in oxidized zones.

Hardness

2-3

Mohs

Luster

Pearly

Streak

Yellow

Transparency

Translucent

mineralrarenull family

Jáchymovite

Hardness: 2-3
Luster: Pearly
Streak: Yellow
Transparency: Translucent

No image

Is this jáchymovite?

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 jáchymovite with a known reference. Jáchymovite sits at Mohs 2-3 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Jáchymovite leaves a yellow streak.
3
Read the luster
Hold the specimen under a strong light. Jáchymovite typically shows a pearly luster.
4
Match the color range
Compare against the expected color range: yellow, yellow-orange, orange.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: microcrystalline crusts, coatings, sprays of thin blades.

Often confused with

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

mineral

Uranopilite

Mohs 2.5

How to tell apart: Streak differs — Jáchymovite leaves yellow, Uranopilite leaves pale yellow.

Often found alongside jáchymovite

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

All properties

Chemical formula: (UO₂)₈(SO₄)(OH)₁₄·~13H₂O
Mohs hardness: 2-3
Density: 4.5 g/cm³
Colors: Yellow Yellow-orange Orange
Streak: Yellow
Luster: Pearly
Transparency: Translucent
Crystal system: Monoclinic
Crystal habit: Microcrystalline Crusts, Coatings, Sprays of Thin Blades
Cleavage: Perfect
Fluorescence: Bright Yellow-green Under UV
Rarity: Rare
Uses: Collector
Host rock: Hydrothermal Uranium-bearing Veins
Typical price: $50-300 per specimen

Where rockhounds find jáchymovite

Classic worldwide localities

Jáchymov, Czech Republic

Field-hunting tip

Look in hydrothermal uranium-bearing veins country — that is the host setting where jáchymovite typically forms. If you start seeing uraninite, uranopilite, zippeite in float, you are in the right ground. Field specimens usually show a microcrystalline crusts, coatings, sprays of thin blades habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify jáchymovite?+

Mohs hardness is 2-3. It typically shows a pearly luster. The streak is yellow. Common colors include yellow, yellow-orange, orange.

Where is jáchymovite found?+

Notable localities include Jáchymov, Czech Republic.

How much is jáchymovite 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 jáchymovite safe to handle?+

This mineral is radioactive. It contains toxic constituents. This mineral is radioactive and contains uranium; handle with care using gloves, avoid inhalation of dust, and store in a sealed container away from living spaces. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like jáchymovite?+

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

What minerals are found with jáchymovite?+

Jáchymovite commonly co-occurs with Uraninite, Uranopilite, Zippeite, Gypsum. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does jáchymovite form in?+

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

What is jáchymovite used for?+

Jáchymovite is used in collector.

Find jáchymovite on the map

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