Mary Margaret

Prospect, Inactive

Alternative names


Commodities and mineralogy

Main commodities Hg
Other commodities Sb
Ore minerals cinnabar; stibiconite; stibnite
Gangue minerals calcite; quartz

Geographic location

Quadrangle map, 1:250,000-scale MG
Quadrangle map, 1:63,360-scale A-4
Latitude 62.164
Longitude -154.873
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Mary Margaret prospect is located along a steep, southeast bank of Cheeneetnuk River, about 1.5 miles (2.4 km) southwest of the airstrip at White Mountain Mercury mine at an elevation of 1,450 feet (442 m) in the SE1/4 sec. 13, T. 24 N., R. 30 W., of the Seward Meridian. Some of the mineralized zone crops out on a ridge about 150 meters south of a conspicuous cold water spring entering the Cheeneetnuk River. The prospect is location 16, of Cobb (1972); the reporter visited the site in 1989 (Alaska Division of Geological and Geophysical Surveys station # 89BT118).

Geologic setting

Geologic description

The Mary Margaret prospect consists of cinnabar, quartz, carbonate and minor stibnite in brecciated limestone of the Early Devonian Cheeneetnuk limestone (Blodgett and Gilbert, 1983). The unit overlies the Dillinger subterrane, a lower Paleozoic continental margin assemblage (Bundtzen and others, 1997).
On the bluff south of the Cheeneetnuk River, two mineralized fracture orientations were measured: (1) a strike of N50E, with a dip of 70SE; and (2) a strike of N65E with a dip of 30SE. The fracture system can be traced for a strike length of about 20 meters before disappearing under vegetation. The cinnabar veinlets average about 5 cm thick and exhibit an exceptional bright red color similar to cinnabar at the Mountain Top Mine described by Miller and others (1989) in the Sleetmute quadrangle.
At the creek level, a cold water sulfur spring that flows from fractured limestone in the area is depositing black, foul-smelling mud that contains Hg. Selected samples of ore contain from 2 to 13 percent mercury and up to 0.5 percent antimony, but with no precious metal values. The cinnabar to stibnite ratio averages about 10 to 1 (T.K. Bundtzen, written communication, 1989).
Geologic map unit (-154.87528417811, 62.1633537086889)
Mineral deposit model Hot Springs mercury? (Cox and Singer, 1986; model 27a?).
Mineral deposit model number 27a?
Alteration of deposit Oxidation of stibnite mineralization to stibiconite.

Production and reserves

Workings or exploration Only surface sampling has been conducted at the prospect. Selected samples contain from 2 to 13 percent mercury and up to 0.5 percent antimony, but no precious metals.
Indication of production None
Reserve estimates None.

Additional comments

The Mary Margaret prospect formed near or in an unnamed strand of the Farewell-Denali fault system (Gilbert, 1981).