Hand sample of the Mount Jackson vitrophyre
By Yellowstone Volcano Observatory
August 2024 (approx.)
Detailed Description
A clean hand sample of the Mount Jackson vitrophyre. This sample has a black, glassy groundmass with large (1–3 mm, or a small fraction of an inch), white phenocrysts suspended in the glass. Photo by Liv Wheeler, Montana State University, August 2024.
Sources/Usage
Public Domain.