Thernardite is an anhydrous sodium sulfate mineral which occurs in arid evaporative environments such as Soda Lake. It fluoresces in a ghostly blue fashion and is best under shortwave ultraviolet light. It phosphoresces blue as well. Only shortwave ultraviolet pictures are posted in addition to a daylight one. Long and Midwave fluorescence are similar but not as vivid as that of shortwave. ISO-100 f/11 1.3 second exposure. 10 ounces 3 x 2 1/4 x 2 inches.