Yooperlites from Pebble beach, Marathon, Ontario

Yooperlites are an uncommon fine to coarse-grained gray igneous rock named syenite. It is composed mainly of alkali feldspar and ferromagnesian minerals such as hornblende.  Yooperlites are very ordinary looking igneous in normal but when exposed to long wave ultraviolet light has a fluorescent mineral is variety of sodalite, which glows orange.

           (Updated) A nicer photo with truer color.  Used my trusty 40 year old Raytech UV light.