Location
The Stehekin mining district, including approximately 380 square miles, occupies the northern end of the county. As defined here it includes part or all of each of the following districts, which at one time or another were considered to be distinct and separate: Doubtful Lake, Stehekin, Horseshoe Basin, Bridge Creek, and Lake Chelan. The composite Stehekin district includes all of the drainage of Stehekin River and all its tributaries. It is bounded on the north and west by the Cascade Range, on the south by the Railroad Creek and Meadow Creek mining districts, and on the east by Sawtooth Ridge. Along the northern and western boundaries is probably the most rugged topography in the state. Elevations range from 1,080 feet at Lake Chelan to 9,080 feet on Buckner Mountain. Many of the peaks are higher than 8,000 feet and most of them are partially covered by glaciers. In spite of the difficulties imposed by topography a road has been built from Stehekin nearly to lower Horseshoe Basin and is nearing completion under the State Mine-to-Market road program. The road connects at Stehekin with boat transportation on the lake, and good Forest Service trails help to open up this naturally inaccessible region.
Geologic Section
Outcropping in many places over the whole district, as in the district to the south, is an old gneiss including several types representing rocks of different origins and different ages. Quartz schists obviously of sedimentary origin are exposed along Maple Creek. Intruding the gneiss and schist are plutonics, some of which are of the younger diorite type found in the Cloudy Pass area to the south. A conspicuous feature of the diorites in this district is a banded phase which in places is to be distinguished with difficulty from the older gneisses of igneous origin. In the eastern part of the district are many wide orthodase-quartz porphyry dikes similar to those with which the copper-gold-silver ores are associated in the Meadow Creek mining district. Over all of the district are many dikes ranging from acidic to basic types.
Ores and Ore Minerals
The ores of the Stehekin mining district are of copper, gold, silver, lead, and zinc. The ore minerals are pyrite, arsenopyrite, chalcopyrite, galena, and sphalerite.
Ore Deposits
Wide, easily seen bands of iron-stained rock are common features on the precipitous slopes high in the mountains throughout the district. These "iron caps" have stimulated vigorous prospecting, and many claims have been staked on them. Under the surface of some of the "iron caps" are copper-gold-silver ores of low grade but possibly rich enough to be mined. These deposits comprise one of two general types which are found in the district. These deposits have chalcopyrite, pyrite, and pyrrhotite in solid masses and in sparse disseminations over wide zones. There are replacements and fillings along shear zones with some hydrothermal alteration of adjacent rock and some silicification along with the ore mineralization. A second kind of ore deposit commonly occurring is the silver-gold-lead-zinc-bearing type quartz veins in which galena, pyrite, and sphalerite are the ore minerals. In these ores galena and pyrite are commonly the most abundant minerals, but in some places sphalerite is present in quantities sufficient to make zinc an important constituent of the ore. The quartz veins in which the sulphides occur are ordinarily of moderate size, and typically they have sharp, well-defined walls with no great amount of alteration in the rocks beside them. The veins in many places have unfilled cavities lined with quartz crystals and partly filled with ore minerals. In some veins the sulphides show pronounced banding, possibly suggesting recurring periods of ore deposition.
Timber and Water
Some of the district is above timber line and much of that below is .occupied by slopes too steep to support a stand of timber. However, the valley bottoms and less precipitous slopes are well forested, so that mine timber, although not available on the ground of some of the mineral properties, is nowhere far distant. Abundant water is available for power development as well as for mining and milling operations.
