Eucryptite is a relatively rare lithium aluminum silicate mineral found almost exclusively in granitic pegmatites. It is most easily identified in the field by its distinct and bright red to pink fluorescence under short-wave ultraviolet light, which helps distinguish it from quartz.
Is this eucryptite?
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 eucryptite with a known reference. Eucryptite sits at Mohs 6.5, 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: white, brown, colorless.
- 5Look at form & habitCrystal system: trigonal. Typical habit: massive, granular, or rarely as small prismatic crystals.
Often confused with
Eucryptite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside eucryptite
Minerals reported to co-occur with eucryptite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- LiAlSiO₄
- Mohs hardness
- 6.5
- Density
- 2.657-2.666 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent to translucent
- Crystal system
- Trigonal
- Crystal habit
- Massive, granular, or rarely as small prismatic crystals
- Cleavage
- {0001} and {1010}
- Fluorescence
- Pink under SW and LW UV
- Rarity
- Rare
- Uses
- Collector, Scientific research
- Host rock
- In lithium-rich pegmatites
Where rockhounds find eucryptite
2 mapped spotsClassic worldwide localities
- Branchville, Fairfield Co., Connecticut, USA
- Center Strafford, Strafford Co., New Hampshire, USA
- Harding pegmatite, Dixon, Taos Co., New Mexico, USA
- Midnight Owl pegmatite, Maricopa Co., Arizona, USA
- Tanco pegmatite, Bernic Lake, Manitoba, and near Nakina, Ontario, Canada
- Bikita, with many other minor localities, Zimbabwe
Field-hunting tip
Where it forms: In lithium-rich pegmatites. If you start seeing albite, spodumene, petalite in float, you are in the right ground. Typical habit: massive, granular, or rarely as small prismatic crystals. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in New Mexico. Start trip planning there.
Common questions
How do you identify eucryptite?+
Where is eucryptite found?+
Can I find eucryptite in the United States?+
What rocks look like eucryptite?+
What minerals are found with eucryptite?+
What kind of rock does eucryptite form in?+
What is eucryptite used for?+
Find eucryptite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
