Thursday, August 27, 2015

The Biggest Gold Nugget In The World

         A gold nugget is a naturally occurring piece of native gold. Watercourses often concentrate nuggets and finer gold in deposits placers. Nuggets are recovered by placer mining, but they are also found in residual deposits where the gold-bearing veins or lodes are weathered. Nuggets are also found in the tailings piles of mining operations. Gold nuggets are usually 20.5K to 22K purity (83% to 92%). Gold nuggets in Australia often are 23K or slightly higher, while Alaskan nuggets are usually at the lower end of the spectrum. Purity can be roughly assessed by the nugget color, the richer and deeper the orange-yellow the higher the gold content. The common impurities are silver and copper, and nuggets high in silver content constitute the alloy
     While nuggets have been found on many goldfields around the world, those from Victoria were particularly large and abundant. From the time of the first goldrushes in the early 1850s, No one knows how many nuggets were found. During the late 1800s, the Mines Department compiled an official list of discoveries and also made models of some of the large nuggets. By the time the reporting system ceased in about 1910, 1300 nuggets over 20 ounces had been recorded. However, almost certainly many more nuggets were found than were recorded, as many discoverers avoided publicity for fear of being robbed. None of the large nuggets found during the goldrushes survived, as all were quickly melted down.
Here is an discovery The biggest gold nugget in the world :

1.  Welcome Stranger Nugget


         The world's largest nugget was found just a couple of inches below the ground near Dunolly, Victoria, Australia on 5 February 1869. Welcome Stranger nugget weighing in at 2,315.5 troy ounces (72.02 kg) The Stranger gold nugget was discovered by John Deason and Richard Oates just 2 inches below the surface near a root of a tree in Bulldog Gully. Due to the size of the nugget it could not be weighed on any scales at the time and had to be broken down into 3 smaller pieces. And then the nugget was soon melted down into ingots and shipped to the Bank of England. In this 1869 illustration published shortly after the discovery, the size of the nugget (61 by 31 cm or 24 by 12 in.) is compared to a 12 inch (30 cm) scale bar. Before 1990, just about all large nuggets were melted down for their monetary value. Today there are less than a dozen known nuggets over 500 ounces. One replica of the "Welcome Stranger" nugget can be found at the City Museum in Treasury Place, in Melbourne, Victoria. The other replica is owned by descendants of John Deason.

2.  Welcome Nugget


      The Welcome Nugget was the name given to a large gold nugget, weighing 2,217 troy ounces 16 pennyweight. (68.98 kg) The original 'Welcome Nugget' was discovered on 9 June 1858 by a group of miners in the Ballart gold fields in Victoria, Australia . At the time it was the largest single piece of natural gold ever found. A little over a year later, the nugget was melted down by the London mint to make gold coins, but models were made beforehand to create replicas like the one seen here. At around 2,217 troy ounces (69 kg), it remains the second largest gold nugget ever found. Because of their scarcity, large nuggets always fetch a price well above their value as precious metal. In 2013, the Welcome Nugget's gold content alone would be valued at nearly $4 million, but an actual specimen of this size and purity would sell for many times this amount. Models of the Welcome Nugget were made and distributed to the Geological and Mining Museum in the Rocks in Sydney, and the Museum of Victoria, as well as the Powerhouse Museum, who purchased models of the Welcome Nugget. Models are also a feature of two displays in Ballarat, the Pioneer Miners (Gold) Monument on the corner of Sturt and Albert Streets in Ballarat Central and at The Gold Museum opposite Sovereign Hill at Golden Point. In the United States, a Replica of the "Welcome Nugget" is exhibited in the Mineralogical Museum at Harvard University in Cambridge, Massachusetts.

3.  Pepita Canaa Nugget


       The Canaã nugget, also known as the Pepita Canaa, was found on Sept 13, 1983 by miners at the Serra Pelada Mine in the State of Para, Brazil. Weighing 60.82 kilograms (134.1 lb; 2,145 oz), it is among the largest gold nuggets ever found,and is, today, the largest in existence. The main controversy regarding this nugget is that the excavation reports suggest that the existing nugget was originally part of a nugget weighing 5,291.09 ounces (150 kg; 331 lb) that broke during excavations. The Canaã nugget is displayed at the Banco Central Museum in Brazil along with the second and third largest nuggets remaining in existence, weighing respectively 1,506.2 ounces (42.70 kg; 94.14 lb) and 1,393.3 ounces (39.50 kg; 87.08 lb), which were also found at the Serra Pelada region.

4.   Blanche Barkly Gold Nugget 

The Blanche Barkly gold nugget discovered In August 1857, by Robert , James Ambrose , Samuel and Charles Napier and this gold nugget , weighing in at 1,743 oz ( 49.41 kilograms ) . The Blanche Barkley nugget was found at a depth of 13 feet, and within 5 feet or 6 feet of holes that were dug three years before.

5.  Precious Gold Nugget


       Precious gold nugget discovered 5 january 1871, by Ah chang and party , this gold nugget weighing in at 1,717 oz ( 48.67 kilograms ) . The 'Precious' nugget was originally obtained at Catto's Paddock, Berlin (now Rheola), west of Bendigo in Victoria. Depth from the surface, 12 feet. Gross weight, 1717 03. Approx. value, 6868 sterling pounds.

6.  Canadian Gold Nugget

Gold was first discovered in Ballarat on the rise above Canadian Creek at the base of Poverty Point aka Golden Point in late August (21-24th) 1851. Reports in the Geelong Advertiser instigated the first rush to the Ballarat Diggings. The Gold Commissioner exercised authority over the newly arrived diggers and friction over mining licences and policing rankled many miners, especially those who could not afford the fee. Canadian gold nugget discovered 31 january 1853 in Canadian Gully , by D, and J. Evans, J, Lees, W. Poulter and W.F.Green , this gold nugget weighing in at 1,319 oz ( 37.39 kilograms ) . Canadian gold nugget was found at a depth of 55 to 60 feet (17 to 18 m).

7.  Lady Hontham Gold Nugget

Lady Hontham weighs 1,177 oz (33.66 kilograms ). and that the nugget had been found by Mc Donald, Irwin, Cock , Radcliffe, McPhillamy, Day, Lyons and Bryant. 8 September 1854. A nugget only 8 dwt. lighter than the last-named (which was known as the Lady Hotham) was discovered in Canadian Gully, Ballarat, at a depth of 60 feet, amongst quartz boulders and wash dirt going an ounce to the ton.

8.  Great Triangle ( aka The Big Triangle ) 


        Great Triangle ( aka The Big Triangle ) which is the largest gold nugget weighs 1,157.6 oz ( 36 kilograms ). Chief Curator Gapanyuk specified that the nugget had been found by one Nikofor Syutkin, a prospector. The nugget was found in 1842 at Tsarevo-Alexandrovsky placer in the Urals location in Ural Mountains. Great Triangle gold nugget its shape approaching the rectangular triangle with the size of the other two sides 27.5 and 31 cm. Nugget thickness of an average of 8 cm is a more or less flat, complex shape of the rock crystal gold.

9.  Golden Eagle Nugget


Golden Eagle nugget weighing in at 1136 oz., found by sixteen year old Jack Larcombe on January 8th, 1931 in Larkinville, Western Australia. The nugget required two men to lift it and was given the name Golden Eagle gold nugget due to its resemblance to a bird.

10.  Sarah Sands Gold Nugget

"The Sarah Sands" nugget was also found at Canadian Gully, Ballarat on the 20th January 1853. It was at a depth of 60 feet and weighed 1,117 oz (31,66 kg). It was associated with quartz. Sarah Sands gold nugget discovered by J.W. Gough, F.J.Sulley and J. Bristow

Tuesday, August 25, 2015

Gold Processing With Method Carbon In Pulp

        Gold processing methods with the Carbon in pulp are often used in large-scale gold mining processing, where the active carbon in pulp method used for recovery of gold ore minerals in the washing tank. Tanks that are used are usually equipped with an agitator and air bubbles equipment and tools are designed to maintain solids in suspension in the slurry, and the achievement of leaching. In the process adsorption ore minerals in the soil material condition of the tank should be good enough to form a slurry that can flow under gravity or when pumped. To form a slurry, mineral ore in the mix with water and the reagent was added to the tank to get the gold leaching reaction

How to work the gold extraction process with carbon adsorption in the pulp can be explained by the following system

Preparation of mineral ore from mines that have been destroyed to obtain a smaller rock with crushing and grinding like a stone or Jaws Crusher Crusher which later can reduce the particle size and liberate gold ore for leaching processes.
        Mineral ore that has undergone a process of destruction and into the refining process by machine Ball Mill to get Ø200 mesh. In the process of natural mineral processing, the size of a Raw materials will greatly influence the outcome and recovery at the end of the process. The more subtle the higher raw material recovery in the can due to leaching in the chlorination process will be the maximum
        Transportation of mineral ore into the first tank made ​​to form a slurry which will be ready at the pump to tank leaching. The use of agitators and H2O in minerals carried out to form a slurry, for pulp which has a density of 1.5 g / cm 3 was diluted to give a pulp that has a density of 1.17. Gold content of about 2 ppm aqueous pulp but obviously fluctuate. Ores containing free gold recovery can not produce high enough to use a single cyanide leaching process, since a very long time for the dissolution of large gold particles.Gold ore containing gold bearing minerals associated with sulphide or carbon require additional treatment, other than size reduction, prior to gold recovery. The addition of cyanide reagents used in the first stage and the pH of the slurry is raised to pH 10 -11 uses chalk, in order to ensure that when cyanide is added, hydrogen cyanide gas is generated and stored in a cyanide solution to dissolve the gold. To create alkaline conditions with pH 10-11 using lime as a pH modifier. Active lime or calcium oxide (CaO) is more reactive raise the pH so it needs a little. However superficial Hydroksida (CaOH) can also be used. pH Modifier others are Coustic Soda or Sodium Hydroxide (NaOH) or Soda Ash (Na2CO3).The concentration of cyanide which is used in a variety of practice 300-500 mg / l (0.03 to 0.05% as NaCN) depending on the ore minerals. Gold was discovered by way of either heap leaching or agitated pulp leaching.
        Results from the first slurry tank at the pump to the tank and leaching. The use of oxygen or peroxygen compound instead of air as an oxidant increases infiltration rates and reduce the consumption of cyanide, because the inactivation of some species consume cyanide present in the slurry. Oxygen gas is often injected under stirring or into the vat to get the desired level of dissolved gases, several base metals plant sulfur dioxide may be sometimes necessary. The addition of chemical reagents for cyanide leaching process is still being done and the ph of the slurry also remain on guard until the pH of 10-11. If the pH is too high will cause the cyanidation process was slow, this is because the cyanide to be too stable in the pulp. Additionally, with too low or too high will cause other metals will dissolve in cyanide compounds that form the complex that also absorbed by activated carbon
      Alkaline conditions (high pH) during the cyanidation process largely determines the success of the process of cyanidation. The use of alkaline such as calcium oxide, will prevent the decomposition of cyanide in solution to form gaseous hydrogen cyanide (HCN.) If the pH is too low / acid can produce volatile HCN gas due to the hydrolysis process, so the concentration cyanide reduced.

CN-(aq) + H + (aq) HCN (g)

        Make sure the pH of 10-11 to anticipate that NaCN does not turn into a very dangerous HCN gas (60 mg of HCN can kill people). Where the conditions of pH 9.3, the concentration of cyanide can be reduced by about 50% since evaporated into a gas HCN, even to 99% changed cyanide HCN at pH 7. In addition to this very dangerous gas would reduce the amount of NaCN dissolved in the slurry so that its ability to dissolve gold is also reduced.
      Oxygen from air is the oxidizing agent to separate the gold in a cyanide solution. Oxygen plays an important role in the process of leaching. In general the higher the oxygen, the reaction is also faster. The use of hydrogen peroxide (H2O2) in a solution of cyanide have been detected in which gold can be separated quickly, and this observation suggests that some gold possible through a separate pair of reactions involving first the formation of hydrogen peroxide: 

2Au + 4CN-+ O2 + H2O → 2 [Au (CN) 2] - + 2OH-+ H2O2
Then hydrogen peroxide reacts with some gold and cyanide.
2Au + 4CN-+ H2O2 → 2 [Au (CN) 2] - + 2OH-

     Then carbon for gold in the uptake of metals added to the tank leaching. Activated carbon of good quality gold production greatly determines the results obtained. Activated carbon is good to have: the structure of the natural pores, a high level of resistance to friction, high hardness levels and form a uniform and have a fairly high CTC. For if the use of activated carbon which has a low CTC, the gold that has been in the activated carbon adsorption will be more easily dislodged during the washing process carbon. CTC is recommended preferably 50% -60%. To produce high-carbon CTC should use a rotating kiln and flat and accurate temperature control. Carbon that has not been through the process kilns typically have only CTC 10-20%. Usually in the CIP method using granular activated carbon with a size of 6x12 or 6x16 mesh, while the size of 6x16 or 12x30 mesh used in the method of CIC. The concentration of carbon in the use of CIP method is 10-25 grams per liter of pulp (0.5 to 1.2% carbon by volume)
      Gold adsorbs onto the surface of the carbon and then passed through a column of carbon and carbon is then filtered by using the screening, the screening of carbon will settle and fine tailings liquid (-100 mesh) will come out through the screen into the tank, which is generally located in step mode , so that the overflow of the highest gravity field which will flow to the next column. Carbon loaded periodically from the column, and then sent to the stripping in place. Carbon pregnant solution is generally heated (200 degrees to 250 degrees F) of (1%) and sodium hydroxide (0.1%) and gold cyanide is re-dissolved and removed from the carbon surface. At this point, a solution of NaOH / CN sent to electrowinning cells, where it will stick to the gold-plated stainless steel cathode. Gold is removed from the cathode by using either high pressure water spray, sometimes shaking the cathode, and in some cases, placed in a stainless steel cathode melting furnace and heated to 2,000 degrees F, to melt the gold from the cathode. Stainless steel cathode, of course, does not melt at this temperature, but this temperature reduces the life of the cathode, and most will wash the gold "sponge" from the cathode. Gold from the powder and then melted until melted and subsequently poured into gold bullion
Once the carbon has been revoked, it can be reused after charging in the kiln, by heating to about 1300 degrees F. carbon is then cooled, filtered and ready for reuse. Generally, various sizes of carbon is 10 mesh to 16 mesh and is almost always no better than 20 mesh. Carbon from coconut shell carbon shell is generally preferred for use in recovering gold from leach solutions.
To obtain optimum results, the processing of gold in rocks oxydis usually quite effective with the mill at 65 mesh and leaching with NaCN 0.05% for 4-24 hours at a density of 50% solids. While rock sulfide require up to 325 mesh refinement and leaching with 0.1% NaCN for 10-72 hours at a density 40% solids. (Weiss 1985)