Westmont gold mine stepping stone for increased production in

Westmont’s parent company Costain’s annual report doesn’t segregate earnings by operation but during a recent visit to Westmont, Michael Richings, vice-president operations, said the mine was “very profitable” and should pay back its original capital this spring. Cash costs are under $200(US) per oz, excluding royalties, he said.

Total cost for mine development including exploration was about $12 million(US) which for that size operation (26,000 oz initially) appears to be a real bargain. Although it was reluctant to say, Westmont is rumored to have sold a good chunk of its production forward at favorable prices which should bolster earnings during this period of weak gold prices.

The company is a subsidiary of Costain Group PLC which is listed on the London Stock Exchange. Over the years the UK-based company has derived most of its income from engineering and construction projects, much of it offshore. But mining (coal and gold) moved into first place in 1987 and mining activities will probably be expanded in the future, possibly through a public company.

Costain is certainly no stranger to mega projects as it holds a 10% interest in the joint venture (Transmanche-Link) constructing the Channel Tunnel between England and France.

Westmont has a fairly large land position in the Jefferson area, a significant portion of it off the immediate mine property, and it has a good-sized budget to explore for additional reserves. The outside properties are leased or owned. The mine property itself is not that big and comprises about 950 acres. Upwards of $1 million will be spent in the southeastern part of the State this year, about half of it locally where the reserve potential is thought to be at least three million tons. Mine life is presently five years and it started with seven years of reserves.

Richings confirmed the company hopes to develop a new gold mine near Ely, Nev., which will add another 40,000 oz of production and could eventually lead to the formation of a publicly-traded company.

Westmont began exploring the Jefferson area in 1983 and completed a feasibility study three years later. A production go-ahead was given in January 1987 and the first gold was produced at the end of July that year. Historically, the region is known for its placer gold production which is often a precursor to hard rock mining.

On a tour of the property Mine superintendent Bill Rose said head grades were averaging about 0.036 oz gold per ton; last year’s average was 0.04 oz and he confirmed they were getting 85% recoveries or better over 90 day s. (South Carolina ores tend to be readily leachable and most of the gold is recovered much earlier). Rose said the ore is quite porous, thoroughly oxidized, blasts well, agglomerates well, and has good percolation. Hot spots in the orebody grade from 0.1 to 0.3 oz and richer sections are generally highly silicified.

The mine is somewhat analogous to the Ridgeway project in at least two ways — grade and recoveries. But Ridgeway is completely conventional, operates at three times the throughput rate, and yields faster recoveries with agitated leaching.

Westmont’s mining rate is approximately 12,000 tons per day of which 5,500 tons is ore. The open pit is on its third pushback and 150,000 tons of broken ore is kept on hand at all times for feedstock. Some of the ore is extremely hard and abrasive so down-the-hole hammers are utilized in conjunction with high pressure compressors (350 psi).

There isn’t much clay in the ore, agglomerated product doesn’t look all that great, but percolation is excellent through 35-ft-high leach piles, said Bob Walsh, mill superintendent. The heaps are situated on asphalt pads which enables loading and unloading and conserves space. A basic radial arm stacker is used to load the pads and its works really well. The asphalt pad is divided into 10 “cells” and it generally takes 15 calendar days to load 50,000 tons and 15 days to unload. The stacker system is interlocked through to the primary crusher and when The Northern Miner visited the property, the company was building up a surge pile so parts of the system could be operated independently.

Unlike Nevada where evaporation rates are often very high, preserving water isn’t necessary at Westmont’s operation. It’s not unusual to have a tropical storm system come in and drop eight inches of water in two days; so a spray system is used on leach pads as opposed to a drip system which reduces evaporation in dryer climates.

Westmont’s carbon plant is presently handling 850 gallons per minute and internal “preg building” is done on leach pads, noted Walish. This increases the dissolved gold content in solution, the net effect being the plant has to handle less solution to produce a given amount of gold. In general, they try to maintain the solution grade at 1 ppm. Carbon is loaded to 100-120 oz per ton and they use pressure stripping and electro-winning to extract the gold. All in all, it’s a neat operation and a good building block for future expansion.

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