Stilbite

specimen number:
2282077

location:
Skookumchuck Dam, Thurston Co., Washington, USA

description:
Loose spray of colorless terminated crystals of stilbite. In great condition, neat thumbnail sized locality example for the species. Collected by Chuck Trantham in 1970. Complete all around.

The Skookumchuck Dam locality, situated along the Skookumchuck River valley in Thurston County, Washington, is a notable mineral occurrence uncovered during infrastructure excavation rather than commercial mining operations. Geologically, the site is hosted within the Eocene-aged basalt flows of the Northcraft Formation, which were heavily blasted during the engineering of the earthen embankment and spillway system. This excavation exposed numerous pocket-bearing basalt zones lined with a distinct suite of secondary minerals, including large mesolite crystal sprays, pink to orange heulandite clusters, stilbite, mordenite, and well-formed analcime crystals. Construction and blasting activities occurred primarily between May 1969 and October 1970, during which time mineral extraction was limited to a brief window by on-site personnel before the geologic exposures were permanently secured and closed to further access.

Charles "Chuck" Trantham is a California-based professional geologist and mineral collector. While serving as the resident project geologist during the construction of the Skookumchuck Dam from 1969 to 1971, he successfully salvaged, documented, and preserved the exceptional zeolite mineral specimens encountered during active blasting before the site was completed and submerged.

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