Felderhof’s Letter to the Editor: No technical reports showed Busang gold was alluvial

I wish to point out one error which somehow crept into “Felderhof’s new life after Bre-X” (TNM, Dec. 31/12–Jan. 6/13). This concerns the comment in brackets: “using gravity concentrate and not alluvial gold, contrary to published technical reports.”

There are no technical reports that state that the gold had an alluvial origin. This is pure speculation by Mr. Graham Farquharson — a mining engineer, not a geologist, geochemist, geophysicist, and foremost, not a petrologist.

Gravity test work was done both on 27 bulk sample by Ore Test in the U.S. and by Normet. Petrologists involved were Dr. Martha Swartz and Dr. Roger Townsend. Neither of them identified alluvial gold. Dr. Roger Townsend studied 10 coarse gold grains. Metallurgically speaking, this refers to any gold whose particle size exceeds 100 microns, or 0.1 mm. The size range at Busang was established at 40 to 170 microns. At Kelian the range was between 20 and 240 microns.

Strathcona Mineral Services submitted over 100 gold grains from one reject sample which assayed 17.6 grams gold per tonne. The range of gold particles was established at 900 to 1,200 microns. This certainly does not fit the Busang picture. Furthermore, in Lakefield’s report to Strathcona it clearly stated that after a sample has gone through the grinding circuit, alluvial gold cannot be distinguished from primary gold. Strathcona simply ignored this fact.

Fineness tests conducted on the Busang gold established the fineness at an average value of 670. This established that the gold came from a primary source. Alluvial gold has a fineness range between 850 and 940, with an average range around 900 to 920.

The second myth widely circulated by Strathcona was that shavings from gold jewellery were added. I saw the photographs which depicted curly, sharp shavings, as when drilling into steel. These shavings were added after [the sample] had gone through the grinding circuit, as this would have totally destroyed its physical characteristics. These gold shavings came from an assay drill hole into a gold doré bar. This was confirmed by a gold expert in Australia.

As an exploration geologist, one has to deal with many unexpected situations. One of the toughest for me was to deal with accidental deaths of my workmates: four in two separate helicopter crashes in PNG, three in a flash flood, two in a landslide, and lastly, the so-called “suicide” in Indonesia.

John Felderhof
The Philippines