Schroff-O'Neil

Mine, Inactive

Alternative names

Newman and Miller
Miller-Newman

Commodities and mineralogy

Main commodities Au
Other commodities Cu; Pb; Te; Zn
Ore minerals altaite; chalcopyrite; coloradoite; galena; gold; nagyagite; pyrite; sphalerite; tetrahedrite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale AN
Quadrangle map, 1:63,360-scale D-7
Latitude 61.811
Longitude -149.299
Nearby scientific data Find additional scientific data near this location
Location and accuracy 2,000 ft east of the end of unimproved road that parallels Craigie Creek. Marked with quarry symbol and labeled 'Schroff-O'Neil Mine' on the Anchorage D-7 1:63,360-scale topographic map. Accurate within 400 ft. Locality 15 of Cobb (1972) and locality 12 of MacKevett and Holloway (1977).

Geologic setting

Geologic description

Mine located on an erosional remnant of a 1 to 6 inch thick quartz vein that cuts the Willow Creek Pluton. The coarsely crystalline quartz vein carries gold; the tellurides nagyagite, altaite, and coloradoite(?); galena in large cubes; pyrite; sphalerite; chalcopyrite; and tetrahedrite. The vein strikes N 70 E and dips 21 to 34 NW. The main vein is crossed by a barren copper-stained quartz vein. Ore deposition was apparently localized at the vein intersections. Nagyagite is an important mineral in that free gold shows a preference to it, especially in the richer ore. Some nagyagite and gold deposition appear to be contemporaneous (Ray, 1954).
The Willow Creek Pluton is a zoned pluton: the outer part consists of hornblende quartz diorite and lesser hornblende tonalite; the core consists of hornblende-biotite granodiorite, and lesser hornblende-biotite quartz monzodiorite and biotite quartz monzonite. Wall-rock alteration within a few inches of the veins is intense, but seldom extends more than 10 to 12 inches beyond the quartz filling. Sericitization and carbonate alteration predominate, but there is some pyritization and in the outer parts of the alteration zone chloritization is present (Ray, 1954).
Geologic map unit (-149.301212353343, 61.8104724941475)
Mineral deposit model Low-sulfide Au-quartz veins (Cox and Singer, 1986; model 36a)
Mineral deposit model number 36a
Age of mineralization Late Cretaceous or younger; vein cuts the Late Cretaceous Willow Creek Pluton.
Alteration of deposit Wall-rock alteration within a few inches of the veins is intense, but seldom extends more than 10 to 12 inches beyond the quartz filling. Sericitization and carbonate alteration predominate, but there is some pyritization and in the outer parts of the alteration zone chloritization is present (Ray, 1954).

Production and reserves

Workings or exploration Developed by 60 ft of open cuts in 1923 (Brooks, 1925). Most of the erosional remnant was mined out by 1950 (Ray, 1954).
Indication of production Yes; small

Additional comments

This mine apparently was originally referred to as the Newman and Miller prospect (Brooks, 1925).

References

MRDS Number A011616
Reporters D.P. Bickerstaff (USGS contractor); S.W. Huss (USGS)
Last report date 7/30/1998