Ludlockite is a rare lead-iron arsenate that typically forms delicate, needle-like acicular crystals or fibrous sprays. It is most famous for its occurrence in the Tsumeb Mine in Namibia, where it displays a vibrant, characteristic orange-red hue.
Is this ludlockite?
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 ludlockite with a known reference. Ludlockite sits at Mohs 1.5-2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Ludlockite leaves a pale brown streak.
- 3Read the lusterHold the specimen under a strong light. Ludlockite typically shows a subadamantine luster.
- 4Match the color rangeCompare against the expected color range: orange-red, red-brown, yellow-orange.
- 5Look at form & habitCrystal system: triclinic. Typical habit: acicular or fibrous radial sprays.
Often confused with
Ludlockite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Carminite is the harder of the two (Mohs 3.5 vs. 1.5-2); streak differs, so Ludlockite leaves pale brown, Carminite leaves reddish yellow; luster reads subadamantine on Ludlockite and vitreous on Carminite.
How to tell apart: Mimetite is the harder of the two (Mohs 3.5-4 vs. 1.5-2); streak differs, so Ludlockite leaves pale brown, Mimetite leaves white; luster reads subadamantine on Ludlockite and resinous to subadamantine on Mimetite.
Often found alongside ludlockite
Minerals reported to co-occur with ludlockite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- PbFe₄As₁₀O₂₂
- Mohs hardness
- 1.5-2
- Density
- 4.33-4.4 g/cm³
- Streak
- Pale Brown
- Luster
- Subadamantine
- Transparency
- Translucent
- Crystal system
- Triclinic
- Crystal habit
- Acicular or Fibrous Radial Sprays
- Cleavage
- Perfect Micaceous On {011}, Perfect On {021}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Hydrothermal Lead-zinc Deposits
Where rockhounds find ludlockite
Classic worldwide localities
- Tsumeb Mine, Namibia
- Ojuela Mine, Mexico
Field-hunting tip
Look in oxidized hydrothermal lead-zinc deposits country, the host setting where ludlockite typically forms. If you start seeing tsumcorite, galena, sphalerite in float, you are in the right ground. Field specimens usually show a acicular or fibrous radial sprays habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find ludlockite on the map
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