Many people don't realize that located 1200 feet below the city of Detriot, Michigan, lies a massive, active, underground salt mine. The Detroit Salt Mine covers and area of more than 1500 acres, and has over 100 miles of underground roads. The salt deposit dates back approximately 400 million years, and resulted from the evaporation of sea water in the Michigan Basin. These photographs show a beautiful specimen of halite (rock salt) collected from the Detroit Salt Mine. Interestingly, halite from this location often shows an orange fluorescent response under UV light, as can be seen in the photographs taken under short wave and mid wave UV light. Note the fluorescent zoning in the cubic crystals. This specimen is not fluorescent under long wave UV. Size 67 x 42 x 21 mm, 38 grams.
Bright orange fluorescence is seen under short wave UV (254 nm).
The mid wave UV (302 nm) response is similar to that seen under short wave UV.
Same specimen, shown under visible light.