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The blasting is hardly heard from the surface. There is one thing which has to be done before blasting. That is to count very carefully the number of cap lamps worn by underground workers to make sure all are evacuated from the underground.
In the past,underground mines were said to be a dark, dirty,dangerous and harsh places to work. However, Hishikari is completely different. To improve working conditions at 200 meters below surface,where the rock temperature goes up to 50°C if not controlled,the air is cooled down by 2,000 liters of cold water and 18,000 cubic meters of fresh air blown into underground. Road sweepers constantly go up and down the tunnels sprinkling water to keep the air clean. |
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How is the mining done?Mining operation starts with the drill holes in the ore body for blasting,The blasting,ore collection and loading onto large dump trucks follow and all these are fully mechanized and manual job is lever handling only. Some machines are remote controlled and heavy works are virtually eliminated. All workers are equipped with a mobile phone called PHS for the security and communication purposes.Says Sato,Manager of Mining Section,"We by no means are satisfied with the current operations. We are now thinking about the operations with remote control system. Is it possible to control underground operations by TV monitors in the booth. Providing a certain distance
between the working places and control room is maintained to enable an immediate response to emergencies, it would be effective from both safety and efficient operations point of view."
Cavities made by the mining are filled with waste rocks that do not contain valuable ore and they must not be left empty,because other tunnels will be affected badly if they collapse. Sato continues,"You must dig very carefully. Recovery has the priority. Our goal is to extract
100%of ore because its gold grade is extremely high." Exploration team is concentrating on discovering new deposits. Ushirone again says,"We are carrying out constantly the underground drilling. When Hishikari first opened,we estimated 120 tonnes of gold reserves. We already have mined 98 tons of gold,however, 166 tonnes of gold still remain unmined according to the latest ore reserve calculations. This is because of a fruitful exploration results and this figure might be even bigger in the future.
Hishikari has a by-product,hot spring. Co-existence and prosperity with the local community is a motto of Hishikari Mines. Hot spring is supplied to the local spa resorts and the remainder is discharged into the river after being cooled down and treated. Hishikari is constantly monitoring water and air quality and noise emission lest the mining operations give environmental damages to the community.
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The gold deposits of Hishikari,forming a straight line from the depths of the earth, boast a grade 10 times that of the average for gold mines worldwide |
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| Sumitomo Metal Mining 's Hishikari Mine,which aims to become a"clean,bright underground factory " (left);dirt is removed from tires at the entrance to prevent dust from being carried into the mine |
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