igneous
Yooperlite (Fluorescent Sodalite-bearing Syenite)
Syenite rich in sodalite
Hardness: 5.5 to 6 on the Mohs scale. Color: Grayish to brownish exterior, but glows a vibrant orange-yellow or bright pinkish-orange under ultraviolet (UV) light due to fluorescent sodalite inclusions. Luster: Vitreous to greasy. Crystal structure: Monoclinic (for feldspars) and isometric (for sodalite).…
- Hardness
- 5
- Luster
- Vitreous to greasy
Identified More igneous →
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Physical properties
Hardness: 5.5 to 6 on the Mohs scale. Color: Grayish to brownish exterior, but glows a vibrant orange-yellow or bright pinkish-orange under ultraviolet (UV) light due to fluorescent sodalite inclusions. Luster: Vitreous to greasy. Crystal structure: Monoclinic (for feldspars) and isometric (for sodalite). Specific gravity: ~2.5 to 2.7.
Formation & geological history
Formed from silica-poor igneous intrusions, primarily alkali-rich magmas. The fluorescent Yooperlites specifically found as glacial erratics along the shores of Lake Superior were transported from the Coldwell Alkaline Complex in Ontario, Canada, dating back to the Precambrian era (approx. 1.1 billion years ago).
Uses & applications
Primarily collected as a novelty and display specimen by rockhounds and mineral enthusiasts using UV (blacklight) flashlights.
Geological facts
First discovered along the shores of Lake Superior in Michigan in 2017 by obsessive rock hunter Erik Rintamaki. The term 'Yooperlite' is a trademarked commercial name for these glowing glacial stones.
Field identification & locations
Easily identified at night using a 365nm UV flashlight along beaches or gravel bars where glacial erratics from alkaline intrusive complexes are deposited. Common locations include the Upper Peninsula of Michigan, USA, and Ontario, Canada.
