Lawrencite is a highly unstable, deliquescent mineral that primarily occurs as a weathering product on iron-nickel meteorites. Collectors often know it as the 'rust disease' that causes meteorites to spontaneously disintegrate by attracting atmospheric moisture and forming acidic solutions.
Is this lawrencite?
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 lawrencite with a known reference. Lawrencite 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: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: greenish brown, white.
- 5Look at form & habitCrystal system: trigonal. Typical habit: crusts, granular, efflorescent.
Often confused with
Lawrencite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Akaganeite is the harder of the two (Mohs 3-4 vs. 2); streak differs, so Lawrencite leaves white, Akaganeite leaves brownish yellow; luster reads vitreous on Lawrencite and adamantine to metallic on Akaganeite.
How to tell apart: Goethite is the harder of the two (Mohs 5-5.5 vs. 2); streak differs, so Lawrencite leaves white, Goethite leaves brownish yellow, yellow-orange, ocher-yellow; luster reads vitreous on Lawrencite and imperfect adamantine metallic to dull earthy; silky when fibrous on Goethite.
Often found alongside lawrencite
Minerals reported to co-occur with lawrencite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- FeCl₂
- Mohs hardness
- 2
- Density
- 3.16 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Trigonal
- Crystal habit
- Crusts, granular, efflorescent
- Cleavage
- {0001}, inferred from crystal structure
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In iron meteorites, presumed to be a terrestrial alteration of meteoritic iron
Where rockhounds find lawrencite
Classic worldwide localities
- Noted in the Tazewell, Ovifak, Canyon Diablo
- Vesuvius, Campania, Italy
Field-hunting tip
Where it forms: In iron meteorites, presumed to be a terrestrial alteration of meteoritic iron. If you start seeing iron, molysite in float, you are in the right ground. Typical habit: crusts, granular, efflorescent. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify lawrencite?+
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Find lawrencite on the map
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