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, 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.
