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Sumdum
Sumdum is a gold mine in the U.S. state of Alaska. It is located on the south side of Endicott Arm, miles inland from Sanford Cove, a small embayment where the town of Sumdum was located.
==Geology==
The country rock in the proximity of the mine is a black graphitic slate, though the schist belt lies a short distance to the east. This slate is usually wrinkled, rich in carbonaceous matter, and scattered throughout are stringers and films of calcite, often carrying particles of pyrite. The mineral deposits are well-defined quartz-filled fissures, striking approximately parallel with the northwest trend of the country rock. They extend for a few hundred feet in a horizontal direction and have been mined to a depth of several hundred feet below their surface outcrops. Two such ledges, which have been largely developed, are known as the Sumdum Chief and the Bald Eagle. The former ledge varies from a surface width of to a narrow vein filling at a depth of . The Bald Eagle ledge, on the other hand, increases from a surface width of to at a depth of . In the latter ledge, the vein changes from a free-milling ore near the surface to a low-grade ore at in depth. Within the quartz bodies, the gold is not uniformly distributed, but is segregated here and there, forming rich pockets, which seem to represent enrichments where the main ledges are intersected by smaller quartz veins. The ore is essentially free gold and gold-bearing pyrite, with small amounts of galena and sphalerite. Quartz and calcite are the gangue minerals, and films of graphite occur between the fillings and the black-slate country.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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