This corundum specimen from Mysore, Karnataka, India is especially rich in brightly fluorescent ruby crystals. The luscious, velvety red response is activated by trivalent chromium, which substitutes for some of the aluminum in the crystal lattice. The matrix shows pale blue-white fluorescence, which contrasts aesthetically against the bright red response of the ruby crystals. This large specimen measures 18.3 x 13 x 6.4 cm and weighs over 2 kg (~4.5 pounds).
Full view of the specimen showing fluorescence under long wave UV (365 nm).
Full view of same specimen shown under visible light. Rasberry red-colored hexagonal crystals of corundum (var. ruby) in a granite-like matrix. This specimen was collected from an unidentified mine in Mysore , India.
Close-up view of the same specimen showing the largest ruby crystal fluorescing red under long wave UV (365 nm). The crystal measures 19.2 mm in length.
Macro view of the largest ruby crystal (19.2 mm in length) shown under visible light. Note the light-colored reaction zone surrounding the crystal.