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
Classic worldwide localities
- Lake Superior shores, Michigan, USA
- Ontario, Canada
Field-hunting tip
Look in syenite country — that is 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.
Common questions
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Find yooperlite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
