This is a typical archaeal environment - Obsidian Pool in Yellowstone National Park. This is a neutral pH boiling hot spring, rich in silica and iron sulfide (pyrite). To us, this looks, and is, deadly inhospitable, but it is rich in archaeal (and bacterial) growth. It is a lot like a "black smoker" environment.
Obsidian pool (informally known as "Jim's Black Pool") is located only about one mile south of the Mud Volcano tourist area of Yellowstone National Park. The pool is in a valley, adjacent to a small lake flanked by woods, and is on the daily bison trail. The area is quite active, with lots of hot springs and solfataras of varying types. Obsidian pool is less than 10 x 30 feet in size, with several boiling areas, and is an opaque black color, like India ink, from the high concentrations of iron and sulfide. The sides of the pool are piled high with course obsidian sand and elemental sulfur. The pool informally bears my name for a trivial reason. I was with the expedition with Sue Barnes and Norm Pace to direct a series of dives in Lake Yellowstone. Sue was working on an entirely separate project on the trip - she hoped to detect primative deep branches of the eukaryotes where they would be predicted to reside; nutrient-rich anaerobic hydrothermal environments, e.g. solfataras. While she was working on a solfatara known informally as "Graceland" (none of the features had formal names at that time, and only Obsidian pool does now), I convinced (nagged) her to take some samples from a nearby pool that seemed to have exactly the hallmarks of the environment that may have harbored the earliest forms of life according to a recent couple of innovative papers. This pool became known as "Jim's Black pool" as a result, and is listed under that name in some of the earliest literature on its microbiology.