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Mine records recovered Geologist receives 65-year old production, assay records from shuttered Cleary Hill mine Patricia Jones Petroleum News Contributing Writer
Recently recovered assay and production records for the Cleary Hill gold mine and mill, dating back to 1938 and 1939, are providing a gold mine of information to assist prospectors currently working the property.
Detailed daily assay and production records show the stamp mill processed gold with grades up to 9.68 ounces per ton. Average grade recorded during that time was 2.35 ounces per ton of rock, says Curt Freeman, owner of Avalon Development, a Fairbanks-based geological consulting firm that has prospected the Cleary Hill mine area for nearly 15 years.
Freeman received a portion of the mine’s records, starting at the end of May in 1938 and concluding at the end of December 1939, from Rudy Vetter, a long-time Alaskan prospector and miner.
Vetter, who processed hard-rock gold ore through the Cleary Hill mill in the early 1960s, found the records while preparing for a personal move, Freeman said.
Mill's recovery averaged 91 percent Contained in a liver-brown manila folder with the company’s stamp on the cover, the hand-scripted records were complied by Leo Saarela, who served as the mine’s head assayer at the time, Freeman said. “He was the guy in charge of what was being produced — in charge of grade control.”
In addition to the high gold grades, Saarela’s records show that the mill’s recovery averaged 91 percent, but at times ranged as high as 99 percent.
“Anything better than 90 percent recovery is Nirvana, by today’s standards,” Freeman said. “Virtually everything that went into the mill came out in the form of a gold bar.”
That’s despite the “rather crude” method of gold recovery used, Freeman said.
At Cleary Hill, ore was crushed by huge stamps inside the mill, then run through an amalgamation circuit to separate the gold from ground rock.
“There was plenty of free gold in the stuff,” Freeman said. “Even so, they tried different methods to increase recovery … jigs and flotation cells. It shows they were high on the curve of technology — nowhere else in Fairbanks had those technologies been employed. They were rather a progressive sort of company.”
Part of Golden Summit Cleary Hill is contained within an exploration property called Golden Summit that Vancouver, British Columbia-based Freegold Ventures has been working since 1991. (See related story.)
By combing through historical mining reports, Freeman previously compiled his best guess for production statistics at Cleary Hill, which started milling in 1908 and ended during World War II.
His past estimate of 281,000 ounces produced at Cleary Hill Mine is probably low, Freeman said. Unfortunately, the recently recovered records don’t include gold production numbers. “So far, we haven’t found that garage file,” he joked.
He does know the mill operated 24 hours a day, processing about one ton per hour, with an average recovery of about 50 ounces of gold every 24 hours.
“By far it was the best run mine in the district,” Freeman said. “They were having a good run when the war caused them to stop.”
After World War II, Cleary Hill faced inflationary problems. In addition, miners hit water in the underground workings, and couldn’t control the flow.
“Clearly they were in ore, and there was still good grade material below what was mined,” Freeman said.
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