Calcite

specimen number:
2292325

location:
Cadman Quarry, Snohomish Co., Washington, USA

description:
An impressive large cabinet piece for this locality with colorless lustrous partly gemmy crystals of rhombohedral calcite to 4.0 cm in size across the top of matrix. In good condition with minimal cleaving present. Crystallized quartz is present throughout.

The Cadman High Rock Quarry, located near Monroe in Snohomish County, Washington, is a major aggregate operation situated on the eastern wall of the Snoqualmie River valley. Geologically, the site is positioned within the southern Whidbey Island fault zone and exposes a complex sequence of Pleistocene glacial and nonglacial units, including the Whidbey Formation and Vashon glacial drift, which overlie shallow Tertiary bedrock. This bedrock belongs to the Mount Persis Andesite, a series of late Eocene volcanic breccias and flows formed approximately 36 to 48 million years ago. Tectonic faulting and brecciation of this andesite created extensive open voids that were subsequently filled by low-temperature hydrothermal fluids. These fluids deposited an array of secondary minerals, making the quarry historically notable among regional mineral collectors for occurrences of banded chalcedony, drusy quartz, calcite, and pseudomorphs after aragonite. Operating since the 1970s, the quarry primarily serves the local Pacific Northwest construction market by processing these glacial gravels and underlying basaltic andesite into industrial crushed stone, sand, and aggregate.

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