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| 2000 Q2 - 2011 Q2 |
礦石品位：礦石中所含元素的百分含量，金銀以「 g/t 」表示每噸礦石含有多少克金或銀。
過去十年，全球白銀產量平均每年增加 2-3%。根據World Silver Survey，在2010年，全球白銀產量達到735萬安士(7.35億)。在2011年上半年，一些主要的白銀生產国增加了产量当其它国家产量下降时。
世界产银量最大的 BHP Billiton’s Cannington，它的銀產量下跌了18%，從2010年上半年的 1890萬安士降到2011年上半年的 1550萬安士，因為受到礦石品位下降的影響。
圖: 藍色是白銀礦石品位；紅線是已開採礦石；左軸是百噸每年；右軸是克每噸
2000年，Cannington 開採 160萬噸的礦石，以平均每噸 636克 (20.45 toz) 的礦石品位，生產出 3000萬安士的白銀。到了2011年，310萬噸的礦石 (增加了93%) 只能產出 500萬安士的白銀。白銀的礦石品位降到了每噸 417克或 13.4 toz (
-34.43%)。
以下是載文:
Over the past decade global silver production has increased on average between 2-3% per year. In 2010, according to the World Silver Survey, global silver production reached 735 million ounces of silver. In the first half of 2011 some of the top silver-producing countries have increased their production while others have seen declines. The top producing silver mine in the world, BHP Billiton’s Cannington, has seen its production decrease from 18.9 million oz in the first half of 2010 to only 15.5 million ounces in the first half of 2011 (an 18% decline). Cannington — like all mines— suffers from falling ore grades.
In 2000, Canningtion mined 1.6 million tons of ore and produced 30 million ounces of silver at an average ore grade of 636 g/t. By 2011, it mined 3.1 million tons of ore (or 92% more) just to produce an additional 5 million ounces than it did eleven years ago.
http://www.marketoracle.co.uk/Article30905.html
