Hummerite is a rare hydrated potassium magnesium vanadate that typically forms as bright orange efflorescent crusts or tiny tabular crystals in oxidized zones of uranium-vanadium deposits. Due to its solubility and sensitivity to atmospheric moisture, specimens should be stored in a dry environment to prevent dehydration or degradation.
Is this hummerite?
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 hummerite with a known reference. Hummerite sits at Mohs 2, 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: pearly.
- 4Match the color rangeCompare against the expected color range: yellow, light orange.
- 5Look at form & habitCrystal system: triclinic. Typical habit: platy, water soluble.
Often confused with
Hummerite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Hummerite leaves yellow, Pascoite leaves cadmium-yellow; luster reads pearly on Hummerite and vitreous to subadamantine on Pascoite.
How to tell apart: Hummerite is noticeably harder (Mohs 2 vs. ~1); streak differs, so Hummerite leaves yellow, Hewettite leaves brownish red; luster reads pearly on Hummerite and silky to adamantine on Hewettite.
Often found alongside hummerite
Minerals reported to co-occur with hummerite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- K₂Mg₂(V₁₀O₂₈)·16H₂O
- Mohs hardness
- 2
- Density
- 2.53 g/cm³
- Colors
- Streak
- Yellow
- Luster
- Pearly
- Transparency
- Translucent
- Crystal system
- Triclinic
- Crystal habit
- Platy, water soluble
- Cleavage
- Perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Leached from vanadium oxide ores and deposited in veins in clay and as efflorescences on bedded or roll-front U-V deposits in sandstone
Where rockhounds find hummerite
Classic worldwide localities
- Hummer mine, Blue Streak mine, Jo Dandy group, and the North Star mine, Paradox Valley, Uravan district, Montrose Co., Colorado, USA
- Mesa No. 1 mine, Lukachukai Mountains, Apache Co., Arizona, USA
- Grants district, McKinley Co., New Mexico, USA
- Corvusite mine, Beaver Mesa, La Sal Mountains, Grand Co., Utah, USA
- Malargüe district, Mendoza Province, Argentina
- Ronneburg deposit, Thuringia, Germany
Field-hunting tip
Where it forms: Leached from vanadium oxide ores and deposited in veins in clay and as efflorescences on bedded or roll-front U-V deposits in sandstone. If you start seeing huemulite, rossite, thenardite in float, you are in the right ground. Typical habit: platy, water soluble. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify hummerite?+
Where is hummerite found?+
Is hummerite safe to handle?+
What rocks look like hummerite?+
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Find hummerite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
