Uraninite is the primary ore of uranium, often appearing as heavy, black, massive or botryoidal crusts. It is intensely radioactive and requires careful handling, storage, and specialized equipment for detection.
Is this uraninite?
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 uraninite with a known reference. Uraninite sits at Mohs 5-6, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: brownish black, gray, olive-green, shining.
- 3Read the lusterHold the specimen under a strong light. Luster: submetallic to greasy, dull.
- 4Match the color rangeCompare against the expected color range: black, brownish-black, gray, grayish black.
- 5Look at form & habitCrystal system: cubic. Typical habit: botryoidal, crystalline, dendritic.
Often confused with
Uraninite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Uraninite leaves brownish black, gray, olive-green, shining, Magnetite leaves black; luster reads submetallic to greasy, dull on Uraninite and metallic to submetallic, may be dull on Magnetite.
How to tell apart: Streak differs, so Uraninite leaves brownish black, gray, olive-green, shining, Hematite leaves cherry-red or reddish brown; luster reads submetallic to greasy, dull on Uraninite and metallic or submetallic to dull on Hematite.
How to tell apart: Luster reads submetallic to greasy, dull on Uraninite and imperfect adamantine metallic to dull earthy; silky when fibrous on Goethite.
Often found alongside uraninite
Minerals reported to co-occur with uraninite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- UO₂
- Mohs hardness
- 5-6
- Density
- 10.63-10.95 g/cm³
- Streak
- Brownish black, gray, olive-green, shining
- Luster
- Submetallic to greasy, dull
- Transparency
- Opaque, transparent in thinnest fragments
- Crystal system
- Cubic
- Crystal habit
- Botryoidal, crystalline, dendritic
- Cleavage
- Good
- Rarity
- Uncommon
- Uses
- Ore of uranium, Collector
- Host rock
- In granite and syenite pegmatites; in hydrothermal high-temperature tin and moderate-temperature Co–Ni–Bi–Ag–As and other sulfide veins; in Colorado Plateau-type sandstone-hosted U–V deposits
Where rockhounds find uraninite
14 mapped spotsClassic worldwide localities
- Branchville, Fairfield Co., Connecticut, USA
- Grafton, Grafton Co., New Hampshire, USA
- Standpipe Hill, Topsham, Sagadahoc Co., Maine, USA
- Spruce Pine, Mitchell Co., North Carolina, USA
- Jáchymov (Joachimsthal) and Horní Slavkov (Schlaggenwald), Czech Republic
- Johanngeorgenstadt, Schneeberg, and Annaberg, Saxony, Germany
Field-hunting tip
Where it forms: In granite and syenite pegmatites; in hydrothermal high-temperature tin and moderate-temperature Co–Ni–Bi–Ag–As and other sulfide veins; in Colorado Plateau-type sandstone-hosted U–V deposits. If you start seeing zircon, monazite, tourmaline in float, you are in the right ground. Typical habit: botryoidal, crystalline, dendritic. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Utah, California, Connecticut. Start trip planning there.
More uraninite photos
Common questions
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Find uraninite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
