The Jensen mine, and the Jackson and Keith prospects as described here are part of a group of 35 claims and properties that were consolidated under the name Marty Group in the 1920s and fell under the control of the Alaska Windham Gold Mining Company in 1930 (Kimble and others, 1984). As defined in this data base, the properties in the claim block include the Fries and Falls Quartz prospects (SD040); the Marty adit (SD041); the Yates and nearby unnamed prospect (SD042); the Yellow Jacket prospect (SD043); and the Jackson prospect, Keith prospect, and the Jensen Mine. These properties are often referred to collectively as the Second Zone as defined by Spencer (1906). The early history of these properties is described in detail by Redman (1988). A small stamp mill was erected on on the south side of Spruce Creek in 1900 and fed by a 3,000-foot aerial tram to the Yellow Jacket prospect; in 1927, a Lane mill, the Marty mill, was erected on the north side of Spruce Creek and tied to the Jensen adit by a 4,400-foot aerial tram. There may have been small test runs of ore through the early stamp mill from one or more of the prospects but the only significant production in the Second Zone is apparently about 50 ounces of gold from the Jensen Mine. In general, the deposits in the Second Zone are gold-quartz veins with few sulfides; the best values are in veins that crosscut muscovite schist of Cretaceous age that generally trends about N30W (Brew and Grybeck, 1984).

The Jackson prospect was active intermittently from 1915 to 1939 (Kimble and others, 1984). The main working is a 58 foot adit. The deposit is a quartz vein that strikes N30W and dips 65SW. The best sample collected by Kimble and others (1984) was a 0.3-foot channel sample that contained 2.5 parts per million (ppm) gold.

The Keith adit was intermittently active from 1915 to 1938. The main working is a 125 foot adit. The deposit is a quartz vein N30W that dips 80NE. The best sample collected by Kimble and others (1984) was a 10-foot channel sample with 2.4 ppm gold.

The Jensen Mine was active in 1927 (and possibly a few more years) and produced most of the lode gold in the Windham Bay area. The main working is a 275-foot drift along the veins, and 50-foot crosscut off the drift. There is a small stope about 30 feet long that was mined for about 30 feet vertically. The Jensen Mine produced 118 tons of hand-sorted ore in 1927. The ore was transported to the Marty mill on Spruce Creek by aerial tram and yielded $1,100 in gold (about 50 ounces). The deposit consists of a series of quartz veins 0.5- to 1.5-feet thick along the main drift. The quartz veins contain pyrrhotite, pyrite, galena, and sphalerite. The main vein is oriented about N55W-60W; others are about N45W-60SW and N45W-70NE. Kimble and others sampled extensively in the Jensen Mine. Eight samples of the main vein averaged about 0.05 ounce of gold per ton. The best sample was a 0.65-foot channel sample that contained 17.8 ounces of gold per ton.