igneous
Yooperlite (Fluorescent Sodalite-bearing Syenite)
Sodalite-bearing Syenite
Hardness: 5.5-6 (Mohs); Color: Mottled gray/black in daylight, glows bright orange/yellow under UV light; Luster: Vitreous to dull; Crystal structure: Isometric (sodalite inclusions); Specific Gravity: 2.5-2.6
- Hardness
- 5
- Luster
- Vitreous to dull
Identified More igneous →
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Physical properties
Hardness: 5.5-6 (Mohs); Color: Mottled gray/black in daylight, glows bright orange/yellow under UV light; Luster: Vitreous to dull; Crystal structure: Isometric (sodalite inclusions); Specific Gravity: 2.5-2.6
Formation & geological history
Formed from molten alkaline magma deep in the Earth's crust (plutonic). The syenite was later transported by glaciers during the Pleistocene epoch and deposited as glacial till/beach stones.
Uses & applications
Primarily used for lapidary work, jewelry, and as a popular collector's specimen due to its unique fluorescence.
Geological facts
While the rock type is scientifically known as sodalite-bearing syenite, the name 'Yooperlite' was trademarked by Erik Rintamaki who 'discovered' them on the shores of Lake Superior in 2017.
Field identification & locations
Identify by using a 365nm long-wave UV flashlight at night; the sodalite inclusions will glow vibrant orange. Commonly found on the rocky beaches of Lake Superior in Michigan's Upper Peninsula.
