Minium is a rare secondary lead mineral formed by the oxidation of galena. It is most often found as a soft, earthy, or powdery coating on other lead ores and is famously known for its vivid orange-red color.
Is this minium?
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 minium with a known reference. Minium 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: yellow-orange.
- 3Read the lusterHold the specimen under a strong light. Luster: dull to slightly greasy.
- 4Match the color rangeCompare against the expected color range: light red, brownish red, vivid red, yellowish red.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: massive, scaly, striated.
Often confused with
Minium vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Minium leaves yellow-orange, Cinnabar leaves scarlet; luster reads dull to slightly greasy on Minium and adamantine, inclining to metallic when dark; dull in friable material on Cinnabar.
How to tell apart: Streak differs, so Minium leaves yellow-orange, Realgar leaves red-orange to red; luster reads dull to slightly greasy on Minium and resinous to greasy on Realgar.
How to tell apart: Hematite is the harder of the two (Mohs 5-6 vs. 2.5); streak differs, so Minium leaves yellow-orange, Hematite leaves cherry-red or reddish brown; luster reads dull to slightly greasy on Minium and metallic or submetallic to dull on Hematite.
Often found alongside minium
Minerals reported to co-occur with minium. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Pb₃O₄
- Mohs hardness
- 2.5
- Density
- 8.9-9.2 g/cm³
- Colors
- Streak
- Yellow-orange
- Luster
- Dull to slightly greasy
- Transparency
- Semitransparent
- Crystal system
- Tetragonal
- Crystal habit
- Massive, scaly, striated
- Cleavage
- Perfect on {110}; perfect on {010}
- Rarity
- Uncommon
- Uses
- Collector, Historical pigment
- Host rock
- A rare secondary mineral in some highly oxidized lead-bearing mineral deposits; may form during mine fires
Where rockhounds find minium
Classic worldwide localities
- Jay Gould mine, Alturas Co., Idaho, USA
- Leadville district, Lake Co., Colorado, USA
- Tonopah-Belmont mine, Osborne district, Maricopa Co., Arizona, USA
- Langhecke, Hesse, Germany
- Badenweiler, Baden-Württemberg, Germany
- Bleialf, Eifel district, Germany
Field-hunting tip
Where it forms: A rare secondary mineral in some highly oxidized lead-bearing mineral deposits; may form during mine fires. If you start seeing galena, cerussite, massicot in float, you are in the right ground. Typical habit: massive, scaly, striated. Train your eye for that shape before scanning the outcrop.
Common questions
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Find minium on the map
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