Our Geology

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Following information gathered from a Washington DNR report on Mines and Minerals by Wayne Moen:

GOLDEN ARROW mines

 The Golden Arrow vein, as exposed in the upper workings, consists of white crystalline quartz that ranges from 6 to 24 inches in width. Much of the quartz has been fractured and then has been re cemented by secondary silica. Parts of the vein, especially at the southwest end of the drift, exhibit brecciation. In order of decreasing abundance, the quartz contains sparsely disseminated pyrite, sphalerite, galena, and chalcopyrite; a small amount of malachite appears on the surface of some quartz fragments. Free gold is present in the quartz but is not generally visible to the unaided eye. Gourlie (oral communication, 1965) reports that some quartz contained particles of gold that were 2 to 3 millimeters in diameter. Some finely divided sulfide minerals occur in dark parallel bands as much as l/2 inch wide in the quartz; these bands tend to parallel the walls of the vein. An assay of this quartz from near the winze in the drift showed 2.00 ounces per ton in gold and 2.50 ounces in silver. This was the highest gold assay on quartz sampled by the writer in the course of this study. Near ground level, fracture surfaces of the quartz vein are rusty brown, due to the oxidation of the iron sulfide minerals.  

ILLINOIS and INDIANA mines

 The main underground adit on the property is 400 feet long and follows a general N. 45° E. course into arkose that strikes N. 15° W. and dips 40° SE.; this adit is now caved at its portal. The dump contains numerous fragments of vein quartz. An assay of this quartz showed 0.30 ounce per ton in gold and 18.54 ounces in silver. The quartz resembles ore from the Indiana and Golden Arrow mines and contains narrow black stringers composed of finely divided particles of pyrite, sphalerite, and galena. Mr. Hyde (oral communication, 1946) stated that quartz from the dump assayed around $350 per ton in gold and silver and that high-grade gold ore was shipped from the mine to San Francisco in 1904. Twelve ounces of 852 fine gold was recovered from % ton of ore. Robert Crandall, of Twisp (written communication, undated), reports as 600 ounces per ton in silver from the vein in the mine. Crandall also states that several veins strike northeastward, dip 80° to the northwest, and consist of 3 to 6 feet of quartz that has a slate footwall and a porphry hanging wall. About 600 feet north of the cabin on the Illinois claim, on the east side of the old wagon road to the Mammoth mine, a 44-inch vein of massive white quartz is exposed. The vein strikes east and dips 74° N.; it can be traced for at least 50 feet on the surface. An adit follows the vein east for about 45 feet, to where the vein pinched to 14 inches and contained marcasite, minor sphalerite, and pyrite (Carithers, field notes, 1944).  About 300 feet south of this vein, on the road to the cabin, an open cut exposes a 10-inch quartz vein that is similar to the 44-inch vein.  

 The country rocks at the Indiana mine are light gray quartzite, argillaceous quartzite, and shale, all of which strike N. 20°-30° E. and dip 40°-55° SE. These rocks contain several shear zones, some of which contain metalized quartz veins and some that offset the veins. The quartz veins range from 1 to 14 inches in width, strike N. 63°-90° E., and dip 45°-80° N. The lower adit, the portal of which is on the Grandview claim, contains 800 feet of underground workings (Fig. 41). It heads S. 69° E. into the hillside and exposes the faulted segments of two quartz veins. At 475 feet in the adit the main vein is offset about 20 feet to the south by a N. 25° W.-trending fault that dips 30° NE. In addition to the quartz, the vein contains calcite and a small amount of disseminated pyrite. From 418 to 448 feet in the drift the vein averages 1.7 feet in width and contains 0.33 ounce per ton in gold and 3.25 ounces in silver (Huntting, field notes, 1946). The upper adit on the Indiana claim is about 400 feet southeast of the lower adit and 135 feet higher in elevation. It is accessible by a trail from the lower adit. The upper adit heads S. 38° E. for 50 feet in argillaceous quartzite, at which point a quartz vein is intersected. This vein, 2 to 10 inches wide, strikes N. 63° E., dips 45° NW., and has been drifted upon for about 135 feet. The vein parallels the bedding of the quartzite wall rock and contains sparsely disseminated pyrite. Near the face of the drift a shear zone that averages 14 inches in width and is 15 feet long contains several narrow quartz stringers. These stringers appear to be an offset segment of the main vein. According to Huntting (field notes, 1946), 125 feet of the vein averages 13 inches in width and contains 0.67 ounce per ton in gold and 2.75 ounces in silver. The 120 tons of ore mined by Hyde from the upper and lower adits averaged $28 to $30 per ton in gold and silver. Although it is not known from which part of the mine the ore in the bunker came, the quartz contains fragments of argillite and sulfide minerals. The sulfide minerals are pyrite, sphalerite, galena, and a small amount of chalcopyrite. One small particle of free gold was seen by the writer.