Selenite from Manitoba, Canada
Contributed by: Michael Crawford
Date: Jun 12th, 2025
Locality: Red River Floodway, Winnipeg, Winnipeg Metro Region, Manitoba, Canada (See on Mindat)
Size: 9 x 11 cm
Description:
Selenite crystal clusters formed in Pleistocene age Lake Agassiz clay. These clusters were found during excavations of the Red River Floodway, Manitoba, Canada that went deep enough to expose the layer in the clay that contain the selenite crystals. The clusters initially form as a ball of intersecting crystals. Larger crystals may form from the center of the ball and extend outward from the ball. These crystals are larger than the crystals in the ball and are often twinned. The twinning shape resembles a duck’s bill. These “duckbill” selenite crystals are only found in the Red River Floodway deposit.
The fluorescence of these selenite crystals is very bright in all wavelengths of UV illumination. There is little variation in the fluorescent color in different wavelengths. The selenite also has strong afterglow in all UV wavelengths. The longwave afterglow is green, and afterglow becomes bluer after shortwave illumination. Organics activate the selenite fluorescence and afterglow.
Summary of luminescence responses:
Gypsum var. Selenite
- Fluorescence under Longwave (365nm LED) UV light: White
- Fluorescence under Midwave (305nm LED) UV light: White
- Fluorescence under Shortwave (255nm LED) UV light: White
- Afterglow after exposure to Longwave (365nm LED) UV light: Green
- Afterglow after exposure to Midwave (305nm LED) UV light: Green
- Afterglow after exposure to Shortwave (255nm LED) UV light: Green