At first glace, this looks like a classic selenite rosette from the Red River Floodway, Manitoba, Canada. But no, guess again! This very similar looking selenite is home-grown here in the USA, from Sheridan Co., Wyoming. Referred to as a "Selenite Flower," this specimen measures 4+ inches in diameter and is notable for the brightness of its fluorescence and phosphorescence under all UV wavelengths.
The above photo montage shows the selenite flower under SW UV (upper left), SW phos. (upper right), LW UV (2nd row, left), LW phos. (2nd row, right), and Visible Light (bottom image).
Close-up view of same specimen shown under visible light. Composed of large, translucent, colorless, plate-like selenite crystals radiating from a darker, spherical, central core of small, tightly-packed, gypsum crystals. The size is 103 x 87 x 53 mm and it weighs 148 grams.
Under short wave UV (254 nm), bright, ghostly, blue-white fluorescence is seen.
Following exposure to short wave UV (254 nm), bright and lasting blue-white phosphorescence is seen.
Under long wave UV (365 nm), bright, ghostly, blue-white fluorescence is seen.
Perhaps the most impressive aspect of this fascinating specimen is the intense green phosphorescence seen after exposure to long wave UV (365 nm).