The fallout itself may appear as dry, ash-like flakes, or as particles too small to be visible; in the latter case, the particles are often deposited by rain. Large amounts of newer, more radioactive particles deposited on skin can cause beta burns, often presenting as discolored spots and lesions on the backs of exposed animals. The fallout from the Castle Bravo test had the appearance of white dust and was nicknamed "Bikini snow"; the tiny white flakes resembled snowflakes, stuck to surfaces, and had a salty taste. 41.4% of the fallout from the Operation Wigwam test consisted of irregular opaque particles, slightly over 25% of particles with transparent and opaque areas, approximately 20% of microscopic marine organisms, and 2% of microscopic radioactive threads of unknown origin.