Dumortierite is an aluminum iron borosilicate mineral that doesn't get much attention in the world of fluorescence, but is a lovely fluorescent species nonetheless. This specimen is from the Dehesa Dumortierite deposit, Alpine, Laguna Mts, San Diego Co., California, and consists of radiating sprays and inclusions of purple-grey dumortierite in a milky quartz matrix. The dumortierite is reactive under short wave UV, and shows a bright blue-white fluorescent response. This specimen measures 73 x 55 x 45 mm, and weighs 192 grams.
In the upper image the dumortierite fluoresces bright blue-white under short wave UV (254 nm). The lower image shows the specimen under visible light.