igneous

Yooperlite (Sodalite-bearing Syenite)

Fluorescent Sodalite-bearing Syenite

Hardness: 5.5-6 (Mohs scale); Color: Gray or mottled black/white in natural light, bright orange-yellow under UV light; Luster: Vitreous to greasy; Crystal Structure: Isometric (for the sodalite component); Specific Gravity: 2.6-2.7

Hardness: 5
Luster: Vitreous to greasy

Identified March 13, 2026More igneous →

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Physical properties

Formation & geological history

These rocks were originally formed through igneous processes in the Canadian Shield (Mesoproterozoic era, roughly 1 billion years ago). They were transported via glacial activity during the last ice age and deposited as glacial erratic stones along beaches.

Uses & applications

Primarily used for lapidary work, jewelry (beads, pendants), and as a popular collector's item for rockhounds.

Geological facts

The name 'Yooperlite' was trademarked by Erik Rintamaki in 2017 after he discovered them on the shores of Lake Superior. While syenite is common, the inclusion of fluorescent sodalite makes these specimens unique; they look like ordinary gray rocks until a 365nm UV light is applied.

Field identification & locations

Identify in the field using a long-wave UV flashlight (365nm) at night; they will glow like glowing embers. Commonly found on the beaches of Lake Superior, especially in Michigan's Upper Peninsula.

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