igneous
Yooperlite
Fluorescent Sodalite-bearing Syenite
Hardness: 5.5-6.0 on Mohs scale; Color: Gray/mottled in daylight, glowing neon orange under 365nm UV light; Luster: Vitreous to dull; Crystal structure: Isometric (sodalite minerals within syenite matrix); Cleavage: Uneven/poor; Specific gravity: Approx. 2.6-2.7.
- Hardness
- 5
- Luster
- Vitreous to dull
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Physical properties
Hardness: 5.5-6.0 on Mohs scale; Color: Gray/mottled in daylight, glowing neon orange under 365nm UV light; Luster: Vitreous to dull; Crystal structure: Isometric (sodalite minerals within syenite matrix); Cleavage: Uneven/poor; Specific gravity: Approx. 2.6-2.7.
Formation & geological history
Formed from alkaline magma cooling slowly deep within the Earth's crust as syenite, which was then enriched with sodalite through hydrothermal processes. These rocks were later transported from Canada's Superior Province to Michigan by glacial movements during the Pleistocene Epoch.
Uses & applications
Primarily used for lapidary work, jewelry making (cabochons), and as a highly sought-after collector's specimen. It has no major industrial or construction use.
Geological facts
Yooperlites were 'discovered' and popularized by Erik Rintamaki in 2017 on the shores of Lake Superior. The 'glow' is caused by the mineral sodalite, which is fluorescent under long-wave ultraviolet light.
Field identification & locations
Identify in the field by scanning rocky shorelines at night using a 365nm UV flashlight; the rocks will pop with a distinct orange glow. Most commonly found along the beaches of Lake Superior in Michigan's Upper Peninsula.
