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 More igneous →
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Physical properties
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
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.
