Hydronováčekite is a rare uranyl arsenate mineral characterized by its distinctive bright yellow, platy crystals. It is typically found in the oxidized zones of uranium deposits and is highly prized by collectors for its strong fluorescence under ultraviolet light.

Hardness

2-2.5

Mohs

Luster

Pearly

Streak

Yellow

Transparency

Transparent

mineralrareAutunite Group family

Hydronováčekite

Hardness: 2-2.5
Luster: Pearly
Streak: Yellow
Transparency: Transparent

No image

Is this hydronováčekite?

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 hydronováčekite with a known reference. Hydronováčekite sits at Mohs 2-2.5, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: yellow.
3
Read the luster
Hold the specimen under a strong light. Luster: pearly.
4
Match the color range
Compare against the expected color range: yellow, greenish-yellow.
5
Look at form & habit
Crystal system: triclinic. Typical habit: platy crystals, micaceous aggregates.

Often confused with

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

mineral

Nováčekite

Mohs 2.5

How to tell apart: Luster reads pearly on Hydronováčekite and waxy on Nováčekite.

How to tell apart: Streak differs, so Hydronováčekite leaves yellow, Autunite leaves pale yellow; luster reads pearly on Hydronováčekite and vitreous, pearly on {001} on Autunite.

Often found alongside hydronováčekite

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

All properties

Chemical formula: H₂Mg(UO₂)₂(AsO₄)₂·n H₂O
Mohs hardness: 2-2.5
Colors: Yellow Greenish-yellow
Streak: Yellow
Luster: Pearly
Transparency: Transparent
Crystal system: Triclinic
Crystal habit: Platy crystals, micaceous aggregates
Cleavage: Perfect basal
Fluorescence: Bright yellow-green under UV light
Rarity: Rare
Uses: Collector
Host rock: hydrothermal uranium-bearing veins

Where rockhounds find hydronováčekite

Classic worldwide localities

Jáchymov, Czech Republic
Schneeberg, Germany
Wölsendorf, Germany

Field-hunting tip

Where it forms: hydrothermal uranium-bearing veins. If you start seeing uraninite, schröckingerite, heinrichite in float, you are in the right ground. Typical habit: platy crystals, micaceous aggregates. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify hydronováčekite?+

Mohs hardness is 2-2.5. Luster: pearly. The streak is yellow. Common colors include yellow, greenish-yellow.

Where is hydronováčekite found?+

Notable localities include Jáchymov, Czech Republic; Schneeberg, Germany; Wölsendorf, Germany.

Is hydronováčekite safe to handle?+

Hydronováčekite contains arsenic and uranium or thorium and calls for real care. Contains uranium and arsenic. Highly radioactive; must be stored in a lead-lined container, kept away from living spaces, and handled with gloves to avoid dust ingestion or skin contact.

What rocks look like hydronováčekite?+

Hydronováčekite is most often confused with Nováčekite, Autunite, Meta-autunite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with hydronováčekite?+

Hydronováčekite commonly co-occurs with Uraninite, Schröckingerite, Heinrichite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does hydronováčekite form in?+

Where it forms: hydrothermal uranium-bearing veins. Working float back to the host body is the standard way to chase a fresh occurrence.

What is hydronováčekite used for?+

Hydronováčekite is used in collector.

Find hydronováčekite on the map

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