Yooperlite is the marketing name for clasts of syenite-rich rocks containing fluorescent sodalite found on the shores of Lake Superior. Under normal daylight, these stones appear as unassuming gray or brownish rocks, but they exhibit a striking bright orange-yellow glow when exposed to ultraviolet light. Collectors typically hunt for these at night along beaches using handheld UV flashlights.
Is this yooperlite?
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 yooperlite with a known reference. Yooperlite sits at Mohs 6, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Yooperlite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Yooperlite typically shows a vitreous to greasy luster.
- 4Match the color rangeCompare against the expected color range: gray, gray-brown.
- 5Look at form & habitCrystal system: cubic. Typical habit: massive, granular.
Often confused with
Yooperlite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside yooperlite
Minerals reported to co-occur with yooperlite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Na₈(Al₆Si₆O₂₄)Cl₂
- Mohs hardness
- 6
- Density
- 2.3-2.4 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous to Greasy
- Transparency
- Translucent
- Crystal system
- Cubic
- Crystal habit
- Massive, Granular
- Cleavage
- Poor
- Fluorescence
- Bright Orange-yellow Under SW and LW UV
- Rarity
- Common
- Uses
- Collector, Lapidary
- Host rock
- Syenite
- Typical price
- $5-50 for small tumbled or rough specimens.
Where rockhounds find yooperlite
22 mapped spotsClassic worldwide localities
- Lake Superior shores, Michigan, USA
- Ontario, Canada
U.S. states with yooperlite
Each link opens a state-specific list of mapped rockhounding spots that produce yooperlite.
Field-hunting tip
Look in syenite country, the host setting where yooperlite typically forms. If you start seeing syenite, microcline, nepheline in float, you are in the right ground. Field specimens usually show a massive, granular habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Michigan. Start trip planning there.
Common questions
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Find yooperlite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
