Location
The Leavenworth mining district includes roughly 515 square miles in southwestern Chelan County, embracing the area drained by Wenatchee River and all its tributaries above Leavenworth with the exception of Chiwawa River. It is bounded on the north by Nason Ridge, the south by Wenatchee Mountains and the Blewett district, and on the east by the Wenatchee and Entiat mining districts. The easternmost part of the district is less rugged than the rest and is better served by roads. Owing to its extreme ruggedness most of the district is not very accessible. Stevens Pass highway, paralleled most of its way by the main line of the Great Northern Railway, leads up the narrow valleys of Wenatchee River and Nason Creek, and a road extends about 25 miles up Icicle Creek from its mouth.
Geologic Section
The northern part of the district is largely covered by Paleozoic argillite, quartzite, and marble. Along the southwestern side of the district serpentine of probable Mesozoic age occupies a narrow belt which is part of the larger belt extending across the Blewett district. The country roc:k of most of the southern part of the district is Mount Stuart granodiorite, which jntrudes the Paleozoic and Mesozoic rocks. The Mount Stuart granodiorite magma may have furnished the mineralizing solutions which made the ore deposits of this area. Along the northeastern side of the district in its less rugged portion the Swauk formation blankets the older rocks. Alluvial terraces and valley fill cover small areas along the larger streams.
Ores and Ore Minerals
The principal ores of the district are of copper, gold, silver, and lead. There are also occurrences of molybdenum and anti- mony ores. The minerals in which these metals occur are chalcopyrite, tetrahedrite, pyrite, pyrrhotite, galena, molybdenite, and stibnite.
Ore Deposits
Although more than 50 mineral claim locations were made on Jack Creek alone in one year very little concerning these and others in the district has ever appeared in print, and since there has been little recent interest in mining in the district not much is known about the nature of the ore deposits there. It appears that the copper, gold, silver, and lead ores all belong in a single genetic group. They occur together in quartz veins cutting serpentine and possibly argillites and quartzites near their contacts with intrusive igneous rocks. 1n at least one property che ore minerals are disseminated throughout the host rock to give a large ore body with irregular boundaries.
Timber and Water
Timber and water for mining and milling purposes are very abundant throughout the district. However, in the vicinity of the known prospects the streams are too small to furnish power for more than the smallest operations.
