Andalusite is a metamorphic mineral common in aluminum-rich rocks, often recognized by its prismatic, squarish crystal habit. The variety chiastolite is well-known for the distinct dark cruciform carbon inclusions visible in cross-sections, making it a favorite for collectors and lapidary work.
Is this andalusite?
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 andalusite with a known reference. Andalusite sits at Mohs 7.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Andalusite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Andalusite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: reddish-brown, brown, pink, gray, yellow.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: prismatic crystals.
Often confused with
Andalusite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside andalusite
Minerals reported to co-occur with andalusite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Al₂SiO₅
- Mohs hardness
- 7.5
- Density
- 3.1-3.2 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Prismatic Crystals
- Cleavage
- Good
- Rarity
- Common
- Uses
- Collector, Lapidary, Industrial
- Host rock
- Metamorphic Rocks
- Typical price
- $5-50 thumbnail, $50-300 cabinet
Where rockhounds find andalusite
8 mapped spotsClassic worldwide localities
- Spain
- Brazil
- USA
- Sri Lanka
- Russia
Field-hunting tip
Look in metamorphic rocks country — that is the host setting where andalusite typically forms. If you start seeing garnet, staurolite, mica in float, you are in the right ground. Field specimens usually show a prismatic crystals habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in South Carolina, California, Maine — start trip planning there.
Common questions
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Find andalusite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
