Doloresite is a rare vanadium oxide mineral primarily found in secondary oxidation zones of sandstone-hosted uranium deposits. It typically presents as dark, brownish-black massive or foliated crusts and is often associated with other vanadium-bearing minerals like corvusite.
Is this doloresite?
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 doloresite with a known reference. Doloresite sits at Mohs 3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: greenish black.
- 3Read the lusterHold the specimen under a strong light. Luster: submetallic; sometimes satinlike on cleavage surfaces.
- 4Match the color rangeCompare against the expected color range: dark brown, black.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: botryoidal, twinning common.
Often confused with
Doloresite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Doloresite leaves greenish black, Corvusite leaves purplish blue-black; luster reads submetallic; sometimes satinlike on cleavage surfaces on Doloresite and “lusterous” on Corvusite.
How to tell apart: Doloresite is noticeably harder (Mohs 3 vs. ~1); streak differs, so Doloresite leaves greenish black, Hewettite leaves brownish red; luster reads submetallic; sometimes satinlike on cleavage surfaces on Doloresite and silky to adamantine on Hewettite.
How to tell apart: Montroseite is the harder of the two (Mohs 5.5-6.5 vs. 3); streak differs, so Doloresite leaves greenish black, Montroseite leaves black.
Often found alongside doloresite
Minerals reported to co-occur with doloresite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- V₃O₄(OH)₄
- Mohs hardness
- 3
- Density
- 3.27-3.33 g/cm³
- Colors
- Streak
- Greenish black
- Luster
- Submetallic; sometimes satinlike on cleavage surfaces
- Transparency
- Opaque, transparent only in thin fragments
- Crystal system
- Monoclinic
- Crystal habit
- Botryoidal, twinning common
- Cleavage
- “Flaky”
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In relatively unoxidized uranium-vanadium ores; from the cores of black, concretionary masses high in uranium and vanadium, surrounded by tyuyamunite-bearing sandstone (La Sal No. 2 mine, Colorado, USA)
Where rockhounds find doloresite
1 mapped spotsClassic worldwide localities
- La Sal No. 2 mine, Lumsden Canyon, Gateway district, and in the Matchless, Arrowhead, Corvusite, Black Mama, and Lumsden No. 2 mines, Mesa Co., Colorado, USA
- Golden Cycle, J.J., and Peanut mines, Montrose Co., Colorado, USA
- Mi Vida mine, San Juan Co., Utah, USA
- A prospect in Valencia Co., New Mexico, USA
- Puttapa zinc mine, near Beltana, South Australia
- Urcal deposit, La Rioja Province, Argentina
Field-hunting tip
Where it forms: In relatively unoxidized uranium-vanadium ores; from the cores of black, concretionary masses high in uranium and vanadium, surrounded by tyuyamunite-bearing sandstone (La Sal No. 2 mine, Colorado, USA). If you start seeing coffinite, uraninite, clausthalite in float, you are in the right ground. Typical habit: botryoidal, twinning common. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Utah. Start trip planning there.
Common questions
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Find doloresite on the map
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