Opal var. Geyersite (rare) Dr. Stillwell Coll.

Item Description

"Geyserite" or siliceous sinter is a variety of opal that is formed in fumarole deposits. This is a lightweight, stream-worn, pebble of this rare material from famous Yellowstone National Park. Older material from the Dr. Stillwell Collection and comes with a faded Wards label. The numbers match. NOTE: Collecting in the park is prohibited today and this is a historic piece with dated label... I could not sell it otherwise