(high-dro-jen-owe-back-ter ass-sid-off-ill-us) is found at some of the hottest regions, often above 60 degrees C. In nature, it takes the forms of filaments which collect together and are visible with the naked eye as white wispy threads. The whiteness in part is due to the inclusion of crystallized sulphur. In culture tends to form curving rods - as seen here. Phase contrast. Material from Dragon Creek, a thermal site in Yellowstone National Park, photograph by Jessie Cristiansen and David Patterson.