Jumbo

Prospect, Inactive

Commodities and mineralogy

Main commodities Au
Ore minerals gold; pyrite

Geographic location

Quadrangle map, 1:250,000-scale JU
Quadrangle map, 1:63,360-scale B-2
Latitude 58.2721
Longitude -134.4199
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Jumbo prospect is at an elevation of approximately 800 feet on Douglas Island, 3/4 mile west of Douglas. It is in the SW1/4NW1/4 section 35, T. 41 S., R. 67 E. of the Copper River Meridian. The location is accurate.

Geologic setting

Geologic description

The Jumbo prospect was discovered in 1922 when native gold was found while sluicing surface trenches. There are four, 200-foot long trenches and a short shaft on the prospect which is in black phyllite and pyritic greenschist (Redman and others, 1989). The pyrite occurs as cubes disseminated in the greenschist. U.S. Bureau of Mines samples contained no significant metal values (Redman and others, 1989).
The rocks in the general area are Upper Jurassic or Cretaceous marine argillite and graywacke, interbedded with andesite or basalt (Brew and Ford, 1985). The bedded rocks are regionally metamorphosed to prehnite-pumpellyite or greenschist grade, and cut by diorite or gabbro dikes and sills.
Geologic map unit (-134.421670471104, 58.2717713505569)

Production and reserves

Workings or exploration The deposit at the Jumbo prospect was discovered in 1922 when native gold was found while sluicing surface trenches. There are four, 200-foot long trenches and a short shaft on the prospect.
Indication of production None

References