History of the Kolmakof Mine
It is thought that the Kolmakof cinnabar deposit was first discovered by Russian explorers in about 1838, making it one of Alaska’s earliest mineral discoveries. A distinguishing characteristic of the deposit is that it is located within a high bluff overlooking the Kuskokwim River; natural erosion action of the river causes cinnabar to become exposed to view by travelers on the river and pieces of fresh cinnabar can be easily collected from the river bank.
Exploration of the deposit dates back to 1881, with small-scale mining occurring from time-to-time. US Government funded exploration activities in the 1950’s and 1960’s failed to locate any significant deposits of cinnabar in the area beyond the original. Formal records and anecdotal evidence indicate that approximately 250 “flasks” worth of mercury has been extracted from KMS cinnabar. A “flask” holds 2½ quarts of mercury and weighs about 76 lbs. In the early days 2 flasks of mercury produced in an on-site home-made retort are recorded to have been sold to local miners for fine gold amalgamation. Most of the mined ore appears to have been shipped to refineries in Tacoma, WA and San Francisco, CA for processing. None of the mining efforts ever proved profitable; the deposit held mercury-rich cinnabar, but not enough of it to justify the high cost of mining and processing.
All of the buildings and equipment found at the KMS today date from the 1940’s and later, most being property of the R&H Mining Company which operated the KMS mining claims from 1965 until closure. The most aggressive mining at the KMS occurred during R&H’s time; they brought in a large bulldozer and used explosives to blast away rock at the top of the bluff to expose and break free cinnabar. The miners hand sorted cinnabar pieces from the rubble, then cleared the debris from the open pit by pushing it over the bluff. A ball mill was employed to crush the ore and a flotation circuit was brought in to further concentrate/purify the cinnabar. R&H conducted some testing of retorting mercury on-site, but since the price of mercury was in steep decline retorting on-site did not get past small scale testing. The last known production of cinnabar occurred in 1970, and the last claims were abandoned and void by 1993.