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using ball mills to extract raw gold from ores

using ball mills to extract raw gold from ores

Placer mining and lode mining are very different. Whereas placer gold has been released from within the rock and is generally free from any significant matrix, lode gold presents different challenges. While gold may be present in ore, it must somehow be released for proper extraction.

As a result, a number of machines have been invented to bring about maximum results with regard to obtaining the much needed resource, gold. One of such equipment is the ball mill. Below is the write-up of how a ball mill works, is used to crush ore and an explanation regarding its effectiveness in gold mining.

First of all, in order to get the best out of how this particular equipment is used it is important to get acquainted with knowledge on what it is, and is made of. Hence, a mill is a piece of equipment used to grind ores. Its major purpose is to perform the grinding and blending of rocks and ores to release any free-gold that is contained within them.

At major mines, the mill was the critical equipment that was required to process the ores that were extracted from deep underground. Many early mines used stamp mills, but many operations today find that ball mills are more functional for smaller operations and perform well with the modern equipment we have available now such as combustion engines.

To perform its functions, the ball mill operates on the principle of impact and attrition. This principle entails that the balls are dropped from near the top of the shell in order to bring about size reduction impact.

The major components of the ball mill include a shell that is hollow and is suspended on its axis to bring about rotation. The axis of the shell can be suspended horizontally or at an angle to the horizontal.

The shell is filled with quite few, but reasonable amount of balls which do the grinding process, and can be made of steel such as chrome steel and stainless steel. They can also be made of ceramic or rubber depending on their targeted material to be ground.

Its major operations are categorized into two, namely the dry and wet processes. Through those processes the machine is able to perform its functions of grinding the crushed materials. One of such functions, is that which is witnessed when grinding different types of ore, such as gold ore.

Now here is what one must know with regard to how the ball mill operates. The drum of the mill (shell) is suspended on two self-aligned rollers. Then the material to be worked on is loaded through the hopper.

From there, the mill is driven using a motor with a clutch, gearbox and the flexible coupling. The mill is then lifted to a certain level of height as it rotates. It is from that height that the balls begin to freely fall or roll down in order to grind the material that has been loaded.

After the material is ground, it is then removed from the mill depending on the discharge method used on the machine. For example, there are center unloading mills as well as unloading through the grille mills.

For the center unloading mills, the ground material is discharged through a hollow unloading trunnion using a free sink. To make it more efficient the pulp level in the drum should at least be above the level of the lower generating trunnion for unloading.

On the other hand, mills whose unloading is done using the grid consist of a lifting device which helps to unload the crushed material. For this reason, in such a mill the slurry level is likely to be lower compared to the unlading trunnion level. In such a mill, a grid with openings used for unloading crushed material is located in the unloading end of the drum.

To crush the gold ore in order to obtain pure gold, the large ore of gold is fed into a jaw crusher or mobile jaw crusher for the primary crushing process. The crushing process acts as a medium of screening the fine gold ore. It is then sieved using the vibrating screen and later sent through the use of a conveyer belt.

The ore is sent into a single-cylinder hydraulic cone crusher for the secondary crushing. Thereafter, the gold ore is transferred to a multi-cylinder hydraulic cone crusher, where the ore is crushed further into finer material. From there, the crushed gold ore is sent to a ball mill, evenly as it passes through a vibrating screen for grinding.

From the ball mill, the gold ore powder is subjected to the process known as beneficiation for further crushing before classification and floatation processes. Most commonly, professional mining operations will use a shaker table at this point. These are extremely effective at capturing tiny particles of free-gold that has been released from the ores.

top 10 biggest gold mines in the united states - report | kitco news

top 10 biggest gold mines in the united states - report | kitco news

1. Carlin. 1,665 koz. Barricks Carlin is the worlds second largest and the US largest gold operation. On July 1, 2019, Barricks Goldstrike (including 60% share of South Arturo) and Newmonts Carlin were contributed to Nevada Gold Mines and are now referred to as Carlin. This gigantic integrated operation located west of the city of Elko on the geologic feature known as the Carlin Trend. Stretching 56km (35mi), the Carlin Trend was first prospected by Newmont geologists John Livermore and Alan Coope in 1965.

2. Cortez. 799 koz. Cortez gold mine is a large gold mining and processing facility in Lander and Eureka County, Nevada, United States, located approximately 75 miles (120 km) southwest of Elko and comprises the Pipeline and South Pipeline deposits and the Cortez Hills deposit. Pipeline and South Pipeline are open pit mines, while Cortez Hills is an underground and open pit mining operation. On July 1, 2019, Cortez was contributed to Nevada Gold Mines, a joint venture between Barrick and Newmont.

3. Turquoise Ridge. 537 koz. Barricks Turquoise Ridge mine is a gold and silver mine located in Humboldt county, Nevada at an elevation of 5,610 feet. Turquoise Ridge is a part of Nevada Gold Mines, a joint venture between Barrick and Newmont.

4. Round Mountain. 324 koz. Kinross Round Mountain is an open-pit mine located in Nevada. Round Mountain uses conventional open-pit mining methods and processes ore by mill and heap leach. Kinross began operating the mine in 2003, and it has since become a continuous improvement leader in the companys portfolio. Round Mountain poured its 15 millionth ounce in 2018. In 2019, Round Mountain poured its first gold bar from the Phase W project.

5. Cripple Creek and Victor. 272 koz. Newmont's Cripple Creek & Victor Mine (CC&V) is located in Teller County, Colorado, southwest of Pikes Peak. CC&V was formed as an operating company for mining operations in 1976, with mining in its Cresson Project starting in 1995. CC&Vs modern, high-tech operations allow for responsible surface mining of various ore types. The majority of the ore is processed in a zero-discharge, valley-type, leach pad to recover gold and silver. In 2015 CC&V commissioned a rod, ball, and flotation mill which processes CC&Vs higher grade, non-oxidized ore.

6. Long Canyon. 261 koz. Barricks Long Canyon mine, located south of Interstate 80 between Wells and West Wendover, Nevada, has been operating as an open surface pit mine since early 2016. Long Canyon is a part of Nevada Gold Mines, a joint venture between Barrick and Newmont.

7. Fort Knox. 238 koz. Fort Knox is one of Kinross largest producing mines and a centre of excellence for the company as one of the few cold weather heap leach facilities in the world. In 2019, the site poured its eighth millionth ounce of gold, over 20 years into its mine life. In 2020, Kinross acquired Manh Choh (formerly Peak Gold) a project expected to commence production in 2024 and process ore at Fort Knox.

8. Marigold. 234 koz. Marigold mine is located in Humboldt and Lander County, Nevada, United States on the Battle Mountain-Eureka trend. SSR Mining completed the acquisition of Marigold on April 4, 2014 and published an updated technical report in July 2018. In production since 1989, Marigold is a large run-of-mine heap leach operation with several open pits, waste rock stockpiles, leach pads, a carbon absorption facility, and a carbon processing and gold refining facility.

9. Phoenix. 205 koz. Barricks Phoenix property is comprised of the Phoenix operations and the Lone Tree operations. Phoenix is an open pit mine in operation since 2006. Lone Tree is an open pit mine in operation since 1991. Phoenix is a part of Nevada Gold Mines, a joint venture between Barrick and Newmont.

10. Bald Mountain. 191 koz. Bald Mountain is an open-pit mine with a large estimated mineral resource base located in Nevada along the southern extension of the prolific Carlin trend, and was acquired by Kinross in January 2016. In October 2018, Kinross acquired the remaining 50% of the Bald Mountain joint venture zone from Barrick Gold to consolidate ownership. The mine is a strong fit with Kinross portfolio and provides opportunities to leverage Kinross' open-pit heap leach expertise. The company expects to continue to develop Bald Mountains upside potential.

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