Mesolite

specimen number:
2133202

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

description:

Delicate acicular colorless sparkling crystals of mesolite coming off matrix. Nice for this classic locality and species.

The Skookumchuk Dam locality, situated near Bucoda in Thurston County, Washington, is a famous site for high-quality zeolite minerals discovered during the construction of the hydroelectric project. Geologically, the minerals occur within the Eocene-aged Hatchet Mountain Formation, which consists of basaltic flow breccias and vesicular volcanic rocks. As mineral-rich groundwater circulated through these volcanic units, it deposited secondary minerals like mesolite, scolecite, and heulandite within the open gas vesicles. Historically, the most significant specimens were recovered during the dam construction period between 1968 and 1970, when massive excavation exposed fresh rock surfaces. While the site is now largely inaccessible due to the completion of the dam and its location on private utility property, it remains legendary among Pacific Northwest collectors for producing aesthetic, needle-like sprays of mesolite that are considered some of the finest in the United States.

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