Pools at Porcelain Basin within Norris Geyser Basin can
contain “mixed” waters with characteristics of both high-
Cl, neutral waters and low-pH acid waters typical of steam-heated areas.
The water appears milky due to the presence of suspended colloidal
opal, a hydrated, poorly crystalline form of silica. Photo by B. Graham
Wall, USGS, taken from a 2 m diameter, helium-filled balloon deployed
in September 2005. Field of view is ~20 meters wide.