Osarizawa Mine in Akita Prefecture, Japan

Osarizawa Underground Mine Adit

Osarizawa mine is an abandoned mine in Akita Prefecture, Japan. Event though the mine is closed, the mine site is kept for sightseeing purposes.  The Osarizawa mine deposit is a vein type deposit  which was  discovered in 708. The oldest Literature of the mine was written in 1599 about the discovery of the Gojumaizawa gold deposit which is part of the mine. The main commodities produced by the mine were gold and copper.

The vein deposit was mined using the shrinkage stope mining method. There are 15 levels and are 30m apart in height. The Total perimeter of the mine levels is 700 km. The area of the mine site is 3km N-S by  2km E-W ~ 6km² . Ceiling is 2-3m in width.   

The Level Zero starts at RL of about 300m and this is where the access adit (ingress) is built.  There are 5 levels above the  zero level and 10 levels below zero level. The mining progressed upwards and mined materials were collected at lower levels with the aid of gravity.

The host rock of the ore deposit is silicate mudstone which is 10 times harder than concrete. Since the host rock is highly competent, the mine was almost unsupported and less artificial support. Few supporting materials used were logs/timbers of about 10mm to 300mm in diameter which were fitted well in between mined out areas to prevent wall collapse. Other artificial supporting methods are roof bolts, Mass wires and steel spiral cables drilled upwards to prevent rocks from falling. Timbers are replaced every 10 years. The other supporting method used was the backfilling of mined out areas with waste materials. Underground water is effectively under control by plastic roofing gutters and drained out along the side of the concrete pathway at each level.

The mined out ore/materials were transported by mini rail cars which are powered by batteries. The rail cars were attached to one another like train cars. The railways were built for these small battery powered rail cars. The drilled or broken ores were loaded onto the rail cars and it required either one or two operators to transport the materials out of the mine via shaft by way of hoisting. At Zero Level the rail cars were driven out via the adit and further to the processing plant for processing.

 Production increased with the increase in the rail cars.

Note:This article is an observation report and may not contain factual and detail information. The information here is kept at high level only. This article is subject to change if need be.

Read More

Rapid PACKTEST

Rapid PACKTEST is commonly known as PACKTEST. This test is a simple onsite method of testing water quality which produces amazing results in a split of a second. It does not require complicated analytical techniques to determine the quality of water. Concentration of heavy metals, precious metals and any other elements and compounds in the water are detected using this method. pH of water can also be determined using this method. Water in this case can be a flowing creek,settling ponds, pool beside vats or heap leach pads, mine pits etc.

     PACKTEST Results for Pihema Creek, 

      Morobe Province.  Cyanide Detected

       (Dark-blue).

The results indicate the concentration of elements intended to test in the water which also influences the pH of water. The readings will give an estimated range of figures and do not have to be exact. Readings are taken with confidence in accuracy of about 90%. To obtain exact results, further laboratory testing is recommended.

It is recommended that Pact Test should be practiced by all government regulators in the extractive industries especially in the Mining and petroleum industry. This will greatly help during statutory inspections which can give results instantly onsite rather than waiting for results in the laboratory after few weeks or months. This will also be a alert for the industry to treat waste water effectively or improve on their waste water treatments and monitoring techniques.

The process and the setup of the testing method are outlined below.

Sampling Procedure for PACKTEST

1.            Fetch water in container and filter the water using syringe and 0.45µm filter to filter water sample and pour filtered water sample into a clear mini cylinder.

2.             Remove the colored line at the top of the tube to clear the aperture.

3.            Press tube's sidewall to expel air, and hold the tube.

4.            Immerse the aperture of the tube into the water sample in the mini cylinder and release to fill the tube halfway.

5.            Shake the tube slowly for few seconds.

6.            Wait for the reaction time as indicated in the instruction manual, and then compare the actual color in the tube with provided Standard Color. The nearest color indicates the concentration value (mg/L = ppm) of the analyte in your sample.

 The above Figure is a simplified diagram by
KYORITSU CHEMICAL-CHECK Lab as a guide.

Note: Cyanide is tested differently. Before the above procedure is applied, first of all dissolve the mixing reagent into the filtered water in a small enclosed translucent cube of about 2cm x 2cm x 1.5cm in size. Finally immerse the cyanide reagent into the solution and release to fill up the tube. Shake the tube and record the reading after 8 minutes.

The reaction times for each element or compound varies from seconds to minutes. Reaction time for cyanide takes longer than any other elements or compounds. It could be other elements or compounds as well but during the tests conducted by the reporter indicated that cyanide took longer than other elements.

It is recommended that PACKTEST should be conducted on site. It would be a bad practice if sample is taken from a different spot and date and tested on different date and location as the results would not represent the sample location and time. If you do then be aware to note the results and anticipate error in the readings recorded.

Other Equipment for testing water quality includes but not limited to pH meter, Turbidity Meter. pH meter is for measuring the pH level of water  and also measure the temperature of water. Turbidity meter measures turbidity of water and also temperature and metal conductivity in the water. 

Turbidity is the measure of suspended particles of sediments flowing under or through the water. It could be steal water or running water.

Read More

Mine Waste Management Training in Japan, 2017

Mine Waste Management Short training sponsored by Government of Japan through JICA in co-orporation with the Government of PNG through CEPA, MRA and DMPGM.

The training lasted two weeks and 6 officers from MRA and CEPA attended the training. The training comprise of theory and practicals and site inspections throughout Japan.

The training was a good exposure and skills acquired will be applied in drafting policies to encourage mining with environment friendly manner.This project will continue till 2018.

Read More

Mercury Pollution and Prevention Measures In Papua New Guinea

Mercury is a heavy silvery-white liquid metal used in some thermometers and barometers. (Symbol: Hg). It is also used to extract fine gold from the mixture of fine sand. Dispose of mercury into the environment is harmful.

Mercury is used in many ways and people do not realize when it gets released into the environment which in turn causes mercury pollution.

In Papua New Guinea almost all Small Scale Miners use mercury in the amalgamation process during gold recovery from the fine sands. Mercury is used in different ways to recover gold. some pour in between the riffles on the sluice boxes in an attempt to capture fine-grained gold.

The contact time between the gold and mercury is not effective for the amalgamation to occur. Often fine gold remains suspended in the flow of particles above the riffles and does not settle to contact the mercury. Thus, about 30  percent (%) of the mercury used in sluice boxes in PNG is released into the river systems. This is actually a treat to the environment.

The Mineral Resources Authority's Small Scale Mining Branch in Wau- Morobe Province try its best to train local miners, especially small-scale miners, on the Safe Use and Handling Of Mercury in the process of amalgamation. The Training Center also trains the miners on other alternatives to be used in the gold recovery process to avoid the use of mercury.

Other alternative methods of gold recovery techniques the small scale miners should be looking at would be Gravity Separation methods in the recovery of fine gold.
Gravity separation methods are vital and the best alternatives to engaged instead of Mercury. Such methods include, but are not limited to:

•  Recovery of Fined Size of gold grain should use Shaking table, Humphreys spiral, Pinced sluices, Reichert cone, etc..
•  Recovery of more finer gold particle should use Nelson concentrator, Falcon concentrator.

The mercury released into the environment is unaccounted for and undetected. Mercury can be detected by a Rapid Pack-test by use of Rapid pack test kits. However, rapid pack test is not available in the country and it is anticipated that pack-test kits will be imported from overseas to use for training and study purposes. 

The next strategy is to ban import of mercury and introduce the alternative gold recovery methods and draft a treatment strategy through research and training. 

Read More