Drive along the public roads and see if it is possible to get pieces of diatomaceous earth. The mine itself is private (no trespassing).
Diatomite Mines (Diatomite Pit North), Quincy, Grant County, Washington, USA(mindat.org) Diatomite - middle Miocene (∼15 Ma) freshwater lacustrine deposit located between flows of the Columbia River Basalt Group.
https://github.com/davepinch/pinchy.cc/blob/master/content/topics/places/mines/diatomite-mines/diatomite-mines.md
On clear days it [Mount Rainier] dominates the southeastern horizon in most of the Seattle-Tacoma metropolitan area to such an extent that locals sometimes refer to it simply as “the Mountain”.