Lawsonite is a characteristic index mineral of the blueschist metamorphic facies, typically forming in subduction zones. Collectors should look for its distinct tabular crystal habits and characteristic blue-tinted appearance within schistose rock matrices.
Is this lawsonite?
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 lawsonite with a known reference. Lawsonite sits at Mohs 8 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Lawsonite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Lawsonite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: colorless, white, bluish-gray, pale blue, gray.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: tabular, prismatic, or massive aggregates.
Often confused with
Lawsonite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Lawsonite is noticeably harder (Mohs 8 vs. 6-7).
How to tell apart: Lawsonite is noticeably harder (Mohs 8 vs. 6-7); luster reads vitreous on Lawsonite and vitreous to pearly on Zoisite.
How to tell apart: Lawsonite is noticeably harder (Mohs 8 vs. 6-6.5).
Often found alongside lawsonite
Minerals reported to co-occur with lawsonite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaAl₂Si₂O₇(OH)₂·H₂O
- Mohs hardness
- 8
- Density
- 3.05-3.12 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Tabular, Prismatic, Or Massive Aggregates
- Cleavage
- Perfect in Two Directions
- Rarity
- Uncommon
- Uses
- Collector, Scientific Research
- Host rock
- Blueschist Facies Metamorphic Rocks
- Typical price
- $10-100 per specimen
Where rockhounds find lawsonite
Classic worldwide localities
- Tiburon Peninsula, California, USA
- Corsica, France
- Guatemala
- New Caledonia
- Valais, Switzerland
Field-hunting tip
Look in blueschist facies metamorphic rocks country — that is the host setting where lawsonite typically forms. If you start seeing glaucophane, pumpellyite, jadeite in float, you are in the right ground. Field specimens usually show a tabular, prismatic, or massive aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find lawsonite on the map
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