Stewart R. Wallace — 1919–2009 - Society of Economic Geologists
Stewart R. Wallace — 1919–2009 - Society of Economic Geologists
Stewart R. Wallace — 1919–2009 - Society of Economic Geologists
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4 SEG NEWSLETTER No 78 JULY 2009<br />
Dear Editor:<br />
Letter to the Editor<br />
Kudos to Peter Laznicka for mining the excellent source <strong>of</strong> discovery data in the Exploration<br />
Reviews section <strong>of</strong> SEG Newsletter (“Metal Resources Announced in 2008: Do They Replenish the<br />
Mined-Out Tonnages?” April 2009, no. 77, p. 23).<br />
The advice in that article to “use more indium!” was based on an incorrect figure in Table 1. World<br />
production <strong>of</strong> indium in 2008 as reported on page 77 <strong>of</strong> USGS Mineral Commodity Summaries 2009<br />
(not Commodity Summaries, 2009) was 568 metric tons (t), not 0.568 t. The 396 t <strong>of</strong> indium discoveries<br />
announced in 2008 is about 70% <strong>of</strong> that year’s world production estimate, not 697 times that<br />
estimate.<br />
The excessive number <strong>of</strong> significant figures and the “Years to last” column heading in that table<br />
help perpetuate the public’s misunderstanding <strong>of</strong> resource numbers. Rather than thinking <strong>of</strong> mineral<br />
resources as stocks in a warehouse, users should be cautioned that the precision expressed in<br />
the world estimates should reflect the uncertainty <strong>of</strong> each <strong>of</strong> the country estimates. Furthermore,<br />
users <strong>of</strong> resource data are sometimes not aware that the effort needed for the acquisition <strong>of</strong> this<br />
information is the result <strong>of</strong> an investment decision by the mining company. An executive <strong>of</strong> a mining<br />
company in Idaho’s Silver Valley underscored this situation when she pointed out that “Lucky<br />
Friday has operated for 50 years, rarely with a projected mine life <strong>of</strong> more than four or five years<br />
based on proven and probable reserves, because <strong>of</strong> the way exploration is conducted from underground.”<br />
(Platts Metals Week, v. 78, no. 53, 31Dec07, p. 3).<br />
The 2008 production <strong>of</strong> 11.34 million metric tons (Mt, not mt; 1 mt = 1 x 10 -3 t = 1 kg) <strong>of</strong> zinc shown<br />
in Table 1 is not from Mineral Commodity Summaries 2009 (MCS 2009); the number there is 11.3<br />
Mt (page 187). MCS 2009 is not the source <strong>of</strong> the estimate <strong>of</strong> world uranium production in 2006; the<br />
Federal responsibility for production statistics for energy minerals was transferred to the<br />
Department <strong>of</strong> Energy in 1977.<br />
The production estimates in the Chromium and Iron Ore chapters <strong>of</strong> MCS 2009 are reported in<br />
thousand metric tons gross weight and in million metric tons <strong>of</strong> “usable ore” (agglomerates, concentrates,<br />
direct-shipping ore, and byproduct ore for consumption), respectively. Comparison with<br />
resources reported as a result <strong>of</strong> exploration presents even greater challenges with these mineral<br />
commodities than with those for which production is reported in terms <strong>of</strong> metal or mineral content.<br />
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