Amphibole, which is a mineral that had previously been used to distinguish Lava Creek Tuff (Yellowstone) members A and B.

Amphibole, which is a mineral that had previously been used to distinguish Lava Creek Tuff (Yellowstone) members A and B.  (a) An amphibole crystal (photo: Rob Lavinsky, iRocks.com – CC-BY-SA-3.0). (b-c) Microscopic images of amphibole crystals from rocks previously assigned to Lava Creek Tuff Member A (b) and Member B (c).  Adapted from Henderson and others (2026), https://doi.org/10.1016/j.jvolgeores.2026.108753.