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| Says Norifumi Ushirone, involved with the exploration of Hishikari: "It is almost impossible to tell how good the grade of a deposit is at the exploration stage. We were truly fortunate to discover such a high grade gold deposit that stretches for over a kilometer" |
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It is not easy to discover high-grade gold deposits. In Hishikari,it was found in a basement rocks which had been considered not to be developed a large deposit according to the traditional geological assumptions. It was the discovery that renewed the convertional theories.Says Norifumi Ushirone,who works at the mine site as an Exploration Manager,"We were very lucky because the ore was of such a high grade." All involved in the project were rejoiced to know that the combination of the technology and the enthusiasm would inevitably lead to success.
Hishikari has two advantages over other gold mines. Firstly fabulously high grade. While world average grade is 5 to 6 grams per tonne,Hishikari 's is 45 to 50 grams. Also ore deposits are world-class vein system with extremely stable high gold value. Secondly,ore deposits lie near the surface,150–250 meters below. Compared with gold mines in South Africa,where the deposits lie 3,000 meters below surface,the cost of mining,transportation, and environmental protection and so on at Hishikari are much lower. In 1997,when 12 years passed since the operations started,the cumulative gold output reached 83.1 tonnes,which made Hishikari a largest gold producer in Japan both in name and reality.
The operations at Hishikari have been extremely smooth. All people concerned point out that the things must have been completely different if the discovery of Hishikari delayed. Because they could inherit the mining technology and know-how from mines such as Besshi (Cu), as described on p.10,Konomai (Au),Sazare (Cu)which had shut down short time before. Hishikari was discovered. Behind the success of Hishikari lies the legacy of mining technology which had been developed in old mines.
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