igneous
Sodalite-rich Syenite (Yooperlite)
Sodalite-rich Syenite (Na8(Al6Si6O24)Cl2 within an igneous matrix)
Hardness: 5.5-6 (Mohs scale); Color: Gray or mottled brown under natural light, fluorescent orange/yellow under UV light; Luster: Vitreous to greasy; Crystal structure: Isometric; Cleavage: Poor.
- Hardness
- 5
- Luster
- Vitreous to greasy
Identified More igneous →
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Physical properties
Hardness: 5.5-6 (Mohs scale); Color: Gray or mottled brown under natural light, fluorescent orange/yellow under UV light; Luster: Vitreous to greasy; Crystal structure: Isometric; Cleavage: Poor.
Formation & geological history
Formed through the cooling of alkaline magma at depth. While syenite is common, the inclusion of fluorescent sodalite in these specific specimens found in the Great Lakes region is associated with glacial transport from the Canadian Shield (Billings Complex).
Uses & applications
Primarily used as a collector's mineral and in lapidary work for jewelry (cabochons) due to its unique fluorescence. Also used for educational geological displays.
Geological facts
These rocks gained mainstream popularity in 2017 when they were 'discovered' and trademarked as 'Yooperlites' in Michigan's Upper Peninsula. They appear as mundane gray rocks until hit with a 365nm long-wave UV light.
Field identification & locations
Identify in the field using a 365nm UV flashlight at night on gravel beaches. Common locations include the shores of Lake Superior in Michigan and parts of Ontario, Canada. Look for a 'glowing coal' effect under the light.
