Unnamed (near Iceberg Point, Lemesurier Island)

Prospect, Inactive

Commodities and mineralogy

Main commodities Cu; Mo
Ore minerals bornite; chalcopyrite; molybdenite
Gangue minerals calcite; epidote; garnet; paligorskite; quartz

Geographic location

Quadrangle map, 1:250,000-scale MF
Quadrangle map, 1:63,360-scale B-1
Latitude 58.263
Longitude -136.076
Nearby scientific data Find additional scientific data near this location
Location and accuracy The occurrence is almost at sea level on Iceberg Point, south of Jacks Cove and west of Willoughby Cove on the south-central coastline of Lemesurier Island. The site is location number 62 of Cobb (1972). It is accurately located within 0.15 mile.

Geologic setting

Geologic description

The occurrence is in limestone of Paleozoic age which, elsewhere on Lemesurier Island, is cut by granitic intrusions. The mineral suite reported at the locality: quartz, garnet, epidote, pyroxene, calcite, molybdenite, chalcopyrite, and bornite (Smith, 1942, p. 177) is a tactite suite, probably related to a nearby intrusion. An unusual asbestos-like mineral, paligorskite, called mountain leather, formed as replacement of limestone near copper-molybdenum bearing vein occurrences. Paligorskite masses reportedly were mined by Joe Ibach.
The site is about three-quarters of a mile east-northeast of the Whitney claims (MF079) another occurrence of copper-molybdenum minerals on the island.
Geologic map unit (-136.077823541811, 58.2626507655445)
Mineral deposit model Distal tactite, suspected intrusion not exposed.
Age of mineralization Cretaceous or younger.
Alteration of deposit Development of tactite in limestone.

Production and reserves

Workings or exploration Surface exposures of copper and molybdenum minerals were explored by trenches and cuts dug by long-time southeast Alaska prospector Joe Ibach, who occasionally lived on the island. The occurrence was first reported by Buddington (1926). It was also listed by Buddington and Chapin (1929) and briefly described by Smith (1942, p. 177).
Indication of production None
Production notes Production of paligorskite, probably as mineral specimens by Ibach.

Additional comments

The prospect is in a carbonate terrane of Paleozoic age. The prospect is in Tongass National Forest and appears to be open for mineral location. Claim activity is unknown.

References