Magnioursilite is a rare secondary uranium mineral that typically forms as soft, earthy, or powdery coatings on other uranium-bearing ores. It is primarily identified in oxidation zones of uranium deposits and requires careful handling due to its inherent radioactivity.
Is this magnioursilite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch magnioursilite with a known reference. Magnioursilite sits at Mohs 2-3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: earthy.
- 4Match the color rangeCompare against the expected color range: yellow, pale yellow.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: powdery, earthy crusts.
Often confused with
Magnioursilite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Magnioursilite leaves yellow, Uranophane leaves yellowish white; luster reads earthy on Magnioursilite and vitreous on Uranophane.
How to tell apart: Streak differs, so Magnioursilite leaves yellow, Boltwoodite leaves white; luster reads earthy on Magnioursilite and pearly; radial aggregates vitreous to silky; dull to earthy in microcrystalline pseudomorphs on Boltwoodite.
Often found alongside magnioursilite
Minerals reported to co-occur with magnioursilite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Mg₄(UO₂)₄(Si₂O₅)₅(OH)₆·20H₂O
- Mohs hardness
- 2-3
- Density
- 3.5-3.8 g/cm³
- Colors
- Streak
- Yellow
- Luster
- Earthy
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Powdery, earthy crusts
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- oxidized uranium deposits
Where rockhounds find magnioursilite
Classic worldwide localities
- Shinkolobwe, Democratic Republic of the Congo
- Jáchymov, Czech Republic
Field-hunting tip
Where it forms: oxidized uranium deposits. If you start seeing uraninite, becquerelite, curite in float, you are in the right ground. Typical habit: powdery, earthy crusts. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify magnioursilite?+
Where is magnioursilite found?+
Is magnioursilite safe to handle?+
What rocks look like magnioursilite?+
What minerals are found with magnioursilite?+
What kind of rock does magnioursilite form in?+
What is magnioursilite used for?+
Find magnioursilite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
