Yooperlite (Syenite clasts with Sodalite)

Physical Properties

Hardness: 5.5-6 on Mohs scale; Color: Mottled gray, tan, and black under normal light; Luster: Vitreous to dull; Crystal structure: Isometric (for sodalite component); Cleavage: Poor; Specific gravity: 2.3-2.6. Key feature is intense orange/yellow fluorescence under UV light.

Formation & Geological History

Formed from alkaline magma reaching the surface and cooling. The specific Michigan specimens are glacial erratics, originally from the Canadian Shield (approx. 1.1 billion years old) and transported by glaciers during the last Ice Age.

Uses & Applications

Primarily used as a collector specimen, in lapidary work for making beads or carvings (like the cat shape shown), and in metaphysical jewelry.

Geological Facts

They were 'discovered' and named by Erik Rintamaki in 2017 on the shores of Lake Superior. While the base rock is Syenite, it is the rich Sodalite inclusions that cause them to glow under long-wave ultraviolet light.

Field Identification & Locations

Identify in the field using a 365nm long-wave UV flashlight at night; they appear as ordinary gray rocks until illuminated. Commonly found on the beaches of Lake Superior in Michigan's Upper Peninsula.

Identified on: 4/29/2026

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