Large spherulites in Hot Creek rhyolite lava in the Long Valley Caldera
![A geologist crouches next to a rhyolite outcrop and points to an egg-shaped mass of radiating pink minerals about the size of a cantaloupe. The rest of the rock is pocked with other egg to grapefruit sized pink crystal masses, interspersed with chunky fragments of black glassy lava.](https://d9-wret.s3.us-west-2.amazonaws.com/assets/palladium/production/s3fs-public/styles/full_width/public/media/images/DSC_1753.png?itok=HgyYI179)
Detailed Description
The presence of spherulites indicates that a lava flow cooled quickly, and their mineralogy holds clues to its precise cooling history. USGS photo by Jessica Ball
Sources/Usage
Public Domain.