igneous
Yooperlite (fluorescent syenite)
Syenite containing fluorescent sodalite, chiefly Na₈(Al₆Si₆O₂₄)Cl₂
AI-generated identification · may be incorrectA rounded, light-gray rock with dark mottling and a bright orange-pink fluorescent patch under ultraviolet light. Sodalite has Mohs hardness 5.5–6; the rock’s hardness varies with its feldspar-rich composition. Its grains are crystalline, with no consistent cleavage visible in the whole specimen.
Identified More igneous →
Explore Yooperlite (fluorescent syenite) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
A rounded, light-gray rock with dark mottling and a bright orange-pink fluorescent patch under ultraviolet light. Sodalite has Mohs hardness 5.5–6; the rock’s hardness varies with its feldspar-rich composition. Its grains are crystalline, with no consistent cleavage visible in the whole specimen.
Formation & geological history
Formed as an intrusive igneous rock when silica-poor magma cooled slowly underground; sodalite crystallized within it. The photographed stone appears water-worn, likely from glacial transport, but its precise age cannot be determined from the image.
Uses & applications
Collected as a UV-fluorescent curiosity and used in lapidary work; polished pieces are sometimes made into jewelry or display specimens.
Geological facts
“Yooperlite” is a trade name for fluorescent sodalite-bearing rocks, popularized after finds along Michigan’s Lake Superior shore.
Field identification & locations
Check with a long-wave UV flashlight in darkness: sodalite-rich patches glow orange to pink. Notable finds occur on Michigan’s Upper Peninsula beaches; avoid assuming every similar gray rock is fluorescent.
