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

Identified March 23, 2026More igneous →

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Physical properties

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.

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Blue Apatite

Fluorapatite (Ca5(PO4)3F)

mineral

Dark Igneous Rock (Likely Basalt or Diabase)

Basalt (extrusive igneous rock) or Diabase (intrusive igneous rock - also known as Dolerite), largely composed of plagioclase feldspar, pyroxene (augite), and sometimes olivine and amphibole. Exact mineralogy would require thin section analysis.

Igneous