Gemini Geyser is located across the road from White Dome Geyser in the Lower Geyser Basin of Yellowstone. In early October 1998, Gemini erupted about every 11 minutes and had a duration of 45 seconds.
Gemini Geyser:

Gemini movie (3.0 Mb, 16 sec, sound)
All images copyright 1998, Michael Frazier. All rights reserved.