Rio Grande Pit

The Rio Grande Pit is a sand and gravel, construction mine located in Jefferson county, Colorado at an elevation of 5,509 feet.

About the MRDS Data:

All mine locations were obtained from the USGS Mineral Resources Data System. The locations and other information in this database have not been verified for accuracy. It should be assumed that all mines are on private property.

Mine Info

Satelite View

MRDS mine locations are often very general, and in some cases are incorrect. Some mine remains have been covered or removed by modern industrial activity or by development of things like housing. The satellite view offers a quick glimpse as to whether the MRDS location corresponds to visible mine remains.

Site Name

Primary: Rio Grande Pit

Commodity

Primary: Sand and Gravel, Construction
Secondary: Gold
Secondary: Silver

Location

State: Colorado
County: Jefferson
District: Golden Area

Land Status

Land ownership: Private
Note: the land ownership field only identifies whether the area the mine is in is generally on public lands like Forest Service or BLM land, or if it is in an area that is generally private property. It does not definitively identify property status, nor does it indicate claim status or whether an area is open to prospecting. Always respect private property.

Holdings

Not available

Workings

Not available

Ownership

Owner Name: Rio Grande Gravel Co.

Production

Not available

Deposit

Record Type: Site
Operation Category: Past Producer
Operation Type: Unknown
Year Last Production: 1973
Discovery Method: Ore-Mineral In Place
Years of Production:
Organization:
Significant: N

Physiography

General Physiographic Area: Interior Plains
Physiographic Province: Great Plains Province
Physiographic Section: Colorado Piedmont

Mineral Deposit Model

Not available

Orebody

Form: TABULAR

Form: TABULAR

Structure

Type: R
Description: Denver Basin, Front Range Uplift

Type: L
Description: Denver Basin

Alterations

Not available

Rocks

Name: Sand and Gravel
Role: Host
Age Type: Host Rock
Age Young: Pleistocene

Analytical Data

Analytical Data: SAMPLE 2 CONTAINED 70 % MAGNETITE, 9.5 % PYRITE, 7 % ZIRCON, 7 % MONAZITE, 2.5 % APATITE, 4 % OTHER.
Analytical Data: SAMPLE 1 CONTAINED 79 % MAGNETITE, 6.5 % ZIRCON, 3.5 % MONAZITE, 3 % APATITE, 1.5 % GARNET, 6.5 % OTHER
Analytical Data: TEST DRILLING BY HUMPHREYS GOLD CORP. IN SECS. 24 AND 25 SHOWED AVERAGE AU SIZE OF 5.7 TO 10 COLORS/MG, BUT ONE HOLE RECOVERED A 16.98-MG NUGGET. TYPICAL SHIPMENT FROM RIO GRANDE PIT CONTAINED 850 FINE IN AU, 147 FINE IN AG, AND 3 FINE IN UNSPECIFIED BASE METALS. PARKER REFERS TO 1936 WRITTEN COMM. FROM KENNETH L. SCHUSSMAN WHO ANALYZED SAMPLES AND FOUND 0.04 COLORS/MG (2.2 WT %) ON PLUS 8 MESH, 0.09 COLORS/MG (4.0 WT %) ON MINUS 8/PLUS 14 MESH, 0.35 COLORS/MG (30.8 WT %) ON MINUS 14/PLUS 28 MESH, 1.8 COLORS/MG (29.4 WT %) ON MINUS 28/PLUS 48 MESH, 15.7 COLORS/MG (16.0 WT %) ON MINUS 48/PLUS 100 MESH, 63.3 COLORS/MG (4.3 WT %) ON MINUS 100/PLUS 170 MESH, 327 COLORS/MG (3.2 WT %) ON MINUS 170/PLUS 325 MESH, 5780 COLORS/MG (10.2 WT %) ON MINUS 325 MESH. ANOTHER 1936 WRITTEN COMM. (FROM K.C. FORCADE) CITES ANALYSIS OF TWO HEAVY MINERAL CONCENTRATES FROM TEST HOLES

Materials

Ore: Sand and Gravel
Ore: Gold

Comments

Comment (Commodity): PLACER GOLD WAS RECOVERED AS BY-PRODUCT OF WASHING/SCREENING OF SAND AND GRAVEL FOR CONSTRUCTION AGGREGATE

Comment (Deposit): AU WAS FOUND CONCENTRATED AT BOTTOM OF UPPER AND LOWER THIRDS OF GRAVEL DEPOSIT

Comment (Location): ALONG CLEAR CREEK AT INDIANA ST. ; INFO FROM LAND.ST :(1975)

References

Reference (Deposit): VAN HORN, RICHARD, 1972, SURFICIAL AND BEDROCK GEOLOGIC MAP OF THE GOLDEN QUADRANGLE, JEFFERSON COUNTY, COLORADO: USGS MAP I-761-A

Reference (Deposit): PARKER, B.H., JR., 1974, GOLD PLACERS OF COLORADO: COLORADO SCHOOL OF MINES QUART., V. 69, NO. 3, P. 63-126

Colorado Mining Photos

Check out this collection of Colorado's best historic mining photos: Incredible Photos of Colorado Mining Scenes.