Ammoniomathesiusite is a rare uranyl sulfate mineral belonging to the mathesiusite group. It typically appears as small, vivid yellow tabular crystals in oxidized uranium-bearing hydrothermal deposits, most notably in Jáchymov. Due to its extreme rarity and radioactivity, it is almost exclusively sought after by advanced mineral collectors specializing in uranium minerals.
Is this ammoniomathesiusite?
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 ammoniomathesiusite with a known reference. Ammoniomathesiusite sits at Mohs 2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: very pale yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: yellow, greenish yellow.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: tabular crystals.
Often confused with
Ammoniomathesiusite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside ammoniomathesiusite
Minerals reported to co-occur with ammoniomathesiusite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (NH₄)₅(UO₂)₄(SO₄)₄(VO₅)·4H₂O
- Mohs hardness
- 2.5
- Density
- 3.672 g/cm³
- Colors
- Streak
- Very pale yellow
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Tetragonal
- Crystal habit
- Tabular crystals
- Cleavage
- Perfect on {110}; good on {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In a U-V roll-front deposit in sandstone; a product of postmining oxidation of a montroseite-corvusite assemblage with pyrite and chalcopyrite
Where rockhounds find ammoniomathesiusite
Classic worldwide localities
- Burro mine, Slick Rock district, southern end of the Uravan Mineral Belt, Colorado Plateau, San Miguel County, Utah, USA
Field-hunting tip
Where it forms: In a U-V roll-front deposit in sandstone; a product of postmining oxidation of a montroseite-corvusite assemblage with pyrite and chalcopyrite. If you start seeing ammoniozippeite, gypsum, jarosite in float, you are in the right ground. Typical habit: tabular crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify ammoniomathesiusite?+
Where is ammoniomathesiusite found?+
Is ammoniomathesiusite safe to handle?+
What rocks look like ammoniomathesiusite?+
What minerals are found with ammoniomathesiusite?+
What kind of rock does ammoniomathesiusite form in?+
What is ammoniomathesiusite used for?+
Find ammoniomathesiusite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
