Black Opal Pool

Overview

Tucked into Biscuit Basin, Black Opal Pool lives up to its name with a dark, opalescent glow that looks almost lit from within. It’s a quick stop on the basin’s boardwalk loop—easy, scenic, and a nice counterpoint to the park’s mega-attractions up the road.

Geology & History

This pool sits in a tight trio with Black Diamond Pool and Wall Pool. All three were created and enlarged by hydrothermal explosions—when superheated water flashes to steam underground and blasts out rock and mud. Black Opal’s crater formed in 1934 and was enlarged in 1953; its evocative name was applied in 1959 for that signature dark opalescence. The neighborhood still reminds you it’s alive: a significant explosion at adjacent Black Diamond Pool on July 23, 2024 lofted muddy water and rocks, reshaping nearby features.

What You’ll See

Expect a compact hot spring with a moody, opaline sheen and clear views from the boardwalk. Around it, Biscuit Basin lines up a sampler plate of springs and small geysers, so you can compare colors and textures in a short walk.

Safety & Closures

Hydrothermal areas can change fast and sometimes erupt without warning. After the 2024 explosion at Black Diamond Pool, Biscuit Basin closed for the remainder of that season, and small muddy bursts continued into 2025 under monitoring. Obey any closures and stay on the boardwalk—this crust is thin.

How to Visit

Biscuit Basin sits about 2.5 miles north of Old Faithful along the Grand Loop Road, across a bridge over the Firehole River. There’s a small, signed parking lot; when it’s full or partially closed, plan to loop back later. There are no services at the feature—use restrooms at Midway Geyser Basin (vault toilets) or the Old Faithful hub (flush toilets).

Best Time to Visit

When open, the boardwalk is accessible around the clock. Crowds tend to swell at midday, with weekday peaks (Tuesday often the highest); early morning or late afternoon bring easier parking and calmer walkways. If you like steam silhouettes, cool mornings make for dramatic photos; for clearer views into the water, aim for lower wind and softer light outside the noon hour.