History of Eddy Gulch Gold Mines
In the 1850s, placer mines in Eddy Gulch produced 150,000 ounces of gold. The source of the placer gold was the series of lode deposits that strike across the head of Eddy Gulch, the principal one being the structure now covered by the Eddy Gulch Group of claims.
The 1925 California State Mineralogist's report states that the placer mines in the North Fork of the Salmon River from Sawyers Bar (Eddy Gulch) to Forks of Salmon, 12 miles down river, produced $25,000,000 in gold. Most of that production occurred when gold was about $12 per ounce, so it represents about 2 million ounces. Based on mine production and vein outcrop extent, the lode mines across the head of Eddy Gulch are the greatest source of gold for this stretch of river. If you attribute only half of that placer production to erosion from Eddy Gulch, a conservative estimate, and add the reported placer production of 150,000 ounces and lode production of 81,352 ounces from mines up Eddy Gulch, that adds up to about 1.23 million ounces of gold. That production represents a snapshot in time, in that the surface outcrop and placer deposits are in essence a moving conveyor belt. Therefore the estimated 1.23 million ounces is a very small fraction of the gold yielded by the apex across Eddy Gulch through recent geologic time. There is no evidence that the deposits will stop yielding comparable gold values with depth (see Geology).
The Mountain Laurel Mine and the Klamath Mine, the greatest producers in Eddy Gulch, were discovered in 1862, and the Union Mine about the same time. The Anna Johnson Mine was discovered in 1895. Reported underground lode production from the Eddy Gulch Group totals 81,352 ounces. 55,319 of those ounces are reported with ore tonnages, allowing a calculation of ore grade (ounces per ton). The 55,319 ounces were extracted from 97,960 tons, averaging an ore grade of 0.565 ounces of gold per ton of ore. This production data is from California State Mineralogist's reports and numerous private geologic reports. However, the production records are far from complete, and so it is assumed that the true production amount was substantially greater than the reported amount. Most of the ore was milled at the Rollin mill site, where a series of mills were constructed during the productive years. Historical records describe nine different mills, including early day arrastras, 5 to 32 stamp, water powered, gravity/amalgamation mills, and the later 25 to 150 ton per day, diesel powered ball/flotation type mills of the 1930s.
Milling has yielded an average 90 percent recovery of gold, often as much as 94 percent, with gravity and amalgamation techniques. 80 percent of the gold occurs free, while 20 percent is in base sulfide ore. The sulfide concentrates have run an average of about 5.0 ounces of gold per ton.