igneous

Sodalite-rich Syenite (Yooperlite)

Sodalite-rich Syenite (Na8(Al6Si6O24)Cl2 within an igneous matrix)

Hardness: 5.5-6 (Mohs scale); Color: Gray or mottled brown under natural light, fluorescent orange/yellow under UV light; Luster: Vitreous to greasy; Crystal structure: Isometric; Cleavage: Poor.

Hardness: 5
Luster: Vitreous to greasy

Identified March 25, 2026More igneous →

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Physical properties

Hardness: 5.5-6 (Mohs scale); Color: Gray or mottled brown under natural light, fluorescent orange/yellow under UV light; Luster: Vitreous to greasy; Crystal structure: Isometric; Cleavage: Poor.

Formation & geological history

Formed through the cooling of alkaline magma at depth. While syenite is common, the inclusion of fluorescent sodalite in these specific specimens found in the Great Lakes region is associated with glacial transport from the Canadian Shield (Billings Complex).

Uses & applications

Primarily used as a collector's mineral and in lapidary work for jewelry (cabochons) due to its unique fluorescence. Also used for educational geological displays.

Geological facts

These rocks gained mainstream popularity in 2017 when they were 'discovered' and trademarked as 'Yooperlites' in Michigan's Upper Peninsula. They appear as mundane gray rocks until hit with a 365nm long-wave UV light.

Field identification & locations

Identify in the field using a 365nm UV flashlight at night on gravel beaches. Common locations include the shores of Lake Superior in Michigan and parts of Ontario, Canada. Look for a 'glowing coal' effect under the light.

Other igneous specimens

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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

Magnetite

Iron(II,III) oxide (Fe3O4)

mineral

Sodalite

Sodalite - Na8(Al6Si6O24)Cl2

mineral

Blue Apatite

Apatite (Group), Ca5(PO4)3(F,Cl,OH)

mineral

Magnetite

Magnetite (Fe3O4)

mineral