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West Quarry, North Table Mountain, Golden, Golden District, Jefferson Co., Colorado, USA

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Latitude & Longitude (WGS84): 39° 46' 31'' North , 105° 13' 24'' West
Latitude & Longitude (decimal): 39.77528,-105.22333
Köppen climate type:Dfb : Warm-summer humid continental climate

The West Quarry is one of only 2 areas now open for collecting on North Table Mountain. It is reached by following Hwy 93 north out of Golden. A locked gate will be on the right, blocking a road which goes by the water tank, and to the top of N. Table Mountain. The quarry is right at the top.

Mineral List

2 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

56 - 66 Ma

ID: 2208849
Potassic basalt (shoshonite) lava flows

Age: Paleocene (56 - 66 Ma)

Description: Dark-gray, porphyritic flow rock containing small pheonocrysts of augite, plagioclase, magnetite, and olivine in a fine-grained matrix. Called mafic latite by Van Horn (1976), although only upper flows are latitic; basal flow is a trachytitic basalt. Formerly mapped as three flows on North Table Mountain and two flows on South Table Mountain (Van Horn, 1976); four total flows now recognized (Drewes, 2004). Clinkery bases and vesicular tops are visible, except on upper flow where top is eroded. Locally forms prominent cliffs. Cavities at some localities contain a variety of zeolite minerals (Ellemeier, 1947). Flows most likely erupted from Ralston Buttes area, about 5 km north of Golden. Interlayered with and considered here as members of Denver Formation. 40Ar/39Ar age of upper flow is 63.9±1.2 Ma (Obradovich, 2002). Flows are as thick as 30 m where they filled channels

Reference: Kellogg, K.S., Shroba, R.R., Bryant, Bruce, and Premo, W.R. Geologic Map of the Denver West 30' x 60' Quadrangle, North- Central Colorado. USGS Geologic Investigations Series 3000. [35]

Early Paleocene
61.6 - 66 Ma

ID: 2446614

Age: Paleocene (61.6 - 66 Ma)

Description: Dark-gray porphyritic lava flows capping North and South Table Mountains and forming dikes near Ralston Reservoir (also includes Flagstaff Mountain sill near Boulder, dated at 64 m.y. by Hoblitt and Larson, 1975). Includes Table Mountain Shoshonite (Scott, 1972) and monzonite and latite of Van Horn (1972). Three flows recognized in North Table Mountain and two flows recognized in South Table Mountain. Total thickness of flows about 73 m. Age of middle flow probably is 63-64 m.y. (Scott, 1972) and age of Ralston Reservoir intrusive is 62 m.y. (Hoblitt and Larson, 1975).

Reference: Trimble, D.E., M.N. Machette. Geologic Map of the Greater Denver Area, Front Range Urban Corridor, Colorado. U.S. Geological Survey Geologic Investigations Series I-856-H. [64]

61.6 - 66 Ma

ID: 2977433
Basaltic flows in Denver Fm near Golden

Age: Paleocene (61.6 - 66 Ma)

Stratigraphic Name: Denver Formation

Lithology: Major:{basalt}

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]

201.3 - 252.17 Ma

ID: 3191821
Mesozoic sedimentary rocks

Age: Triassic (201.3 - 252.17 Ma)

Lithology: Sedimentary rocks

Reference: Chorlton, L.B. Generalized geology of the world: bedrock domains and major faults in GIS format: a small-scale world geology map with an extended geological attribute database. doi: 10.4095/223767. Geological Survey of Canada, Open File 5529. [154]

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

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