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Robertson pit (Robertson Quarry), Dayton, Mason Co., Washington, USA

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Latitude & Longitude (WGS84): 47° 11' 30'' North , 123° 16' 23'' West
Latitude & Longitude (decimal): 47.19194,-123.27333
Köppen climate type:Csb : Warm-summer Mediterranean climate

A traprock quarry in Eocene submarine pillow basalt of the Crescent formation. Owned by Simpson Timber Co., Shelton, WA. Located 3.5 miles SW of Dayton.

Mineral List

5 valid minerals.

Regional Geology

This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.

Click on geological units on the map for more information. Click here to view full-screen map on

0.0117 - 2.588 Ma

ID: 1435083
mostly Vashon Stade in western WA; unnamed in eastern WA

Age: Pleistocene (0.0117 - 2.588 Ma)

Lithology: Continental glacial till, Fraser-age

Reference: Washington State Department of Natural Resources, Division of Geology and Earth Resources. Washington Interactive Geologic Map: 1:100,000 scale. Washington Division of Geology and Earth Resources. [19]

0.0117 - 2.588 Ma

ID: 2999700
Younger glacial drift

Age: Pleistocene (0.0117 - 2.588 Ma)

Stratigraphic Name: Vashon drift; Possession Drift; Whidbey Formation

Description: Younger glacial drift, undivided. Till, outwash, and associated deposits; sorted and unsorted sand, gravel, silt, and clay. Includes some alluvium.

Comments: Includes nonglacial sediments and peat beds locally. Example: Whidbey Formation in Central Puget Lowland; peat beds in Vashon Stade. Principally Wisconsin in age. Difficult to distinguish from Qg2 by lithology; distinction is in age difference only. Some stratigraphic units may occur in both units, regardless of age.

Lithology: Major:{fine alluvium,coarse alluvium}

Reference: Horton, J.D., C.A. San Juan, and D.B. Stoeser. The State Geologic Map Compilation (SGMC) geodatabase of the conterminous United States. doi: 10.3133/ds1052. U.S. Geological Survey Data Series 1052. [133]

Data and map coding provided by, used under Creative Commons Attribution 4.0 License

This page contains all mineral locality references listed on This does not claim to be a complete list. If you know of more minerals from this site, please register so you can add to our database. This locality information is for reference purposes only. You should never attempt to visit any sites listed in without first ensuring that you have the permission of the land and/or mineral rights holders for access and that you are aware of all safety precautions necessary.


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Lasmanis, R. (1988) Minerals of the Crescent Formation, Robertson Pit, Mason County, Washington. Rocks & Minerals, V 63, pp. 24-28.
Tschernich, R.W. (1989) Notes on the zeolites from the Robertson Pit, Dayton, Mason County, Washington. Micro Probe, V 6, No. 8, p. 15.
Tschernich, R.W. (1992) Zeolites of the World. Geoscience Press, Phoenix, Arizona.

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