Heulandite

specimen number:
2133347

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

description:
Light pink lustrous crystals of heulandite attractively covering matrix. In great condition. Collected by Chuck Trantham in 1969.

The Skookumchuck Dam site, located in Thurston County, Washington, involved extensive quarrying and excavation operations to construct a major earthen embankment on the Skookumchuck River. Geologically, the site cuts into the Eocene-aged Northcraft Formation, which consists of thick basaltic lava flows. Blasting for the dam abutments and spillway exposed major vesicle pockets within the basalt that contained exceptional suites of secondary zeolite and silicate minerals, including well-crystallized analcime, heulandite, mesolite, and stilbite. Industrial excavation and quarrying of approximately 2.2 million cubic yards of earthfill from the surrounding hills occurred between May 1969 and October 1970 under ownership of the Pacific Power and Light Company. While active engineering extraction ceased upon the completion of the dam in late 1970, the site remains historically notable for the volume of mineral specimens recovered by geologists during the brief construction window.

Charles C. Trantham was a prominent California mineral collector, field collector, and geologist whose active field exploration spanned the mid-to-late 20th century. Professionally trained as an engineering geologist, he combined his formal scientific background with a deep passion for field mineralogy, leading him to explore and document numerous remote localities throughout California, Nevada, and the Pacific Northwest. He was widely recognized within the mineralogical community for his methodical approach to collecting, keeping meticulous records of his field discoveries, and assembling an extensive, highly regarded private collection of Western North American minerals. Trantham frequently contributed to the field by discovering or providing rare research material to academic mineralogists, and his legacy is preserved today through the high-quality specimens bearing his original handwritten labels that reside in major private collections and museum archives.

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