Black Opal Pool’s past can be read in the boulders that are scattered around the spring. Tremendous steam explosions rocked the site in 1934. In 1937, and again in 1947 and 1948, Black Opal Pool erupted in single bursts of 20 to 30 feet. 1953 saw the last major eruptions. The general area saw a resurgence of activity in 2006, when nearby Black Diamond Pool erupted powerfully and some new but small geysers made their first appearance. Black Opal Pool is now a beautiful opalescent blue, and it fosters a large and colorful community of heat-loving bacteria and plants below its eastern end.
The February 2012 issue of the Geyser Gazer Sput mentions a "visitor report" of a Black Opal eruption in January 2012. We have no other information on this event, which may have been another Black Diamond eruption. As of spring 2017, water (hot but not boiling) is reported to be draining into Black Opal's pool from Black Diamond's, so this geyser may be dormant until something happens either to heat it up or to stop the quenching flow.