Yearly Archives: 2011

Discoloration of silver

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When silver is exposed to air, the air oxidizes the silver, causing it to discolor. This tarnish is caused by contact with sulfur compounds such as hydrogen sulfide in the air. Some items that can cause tarnishing in silver include some paints, carpet padding, wool, felt, fuel, rubber bands and latex gloves. Some foods too, can affect the color of silver, especially eggs, onions and mayonnaise. Humidity and moisture can change silver’s color, as well as oily salts from fingers.

Careful handling and storage of silver can help prevent tarnishing. Storing silver in a moderate, controlled environment with low humidity works best. Numismatic, collectable coins should be stored in containers specially made for coin storage. Handling silver coins requires wearing white cotton gloves.

Removing tarnish from silver is not difficult. Try to catch it early, as it is more easily removed before it turns to light brown or black. With light tarnish, use a vinegar-based window cleaner or a liquid, non-abrasive, unscented hand sanitizer that contains no aloe. Rub it on gently with cotton balls, then dry with a cotton dish towel. This is the least abrasive method for cleaning sliver, although it shouldn’t be used on numismatic coins.

With silver coins, experts recommend that they be professionally cleaned. Coin dealers and collectors want to buy coins in their original condition. Removing tarnish from coins can harm the coins, leaving spots and scratches. However, if you must clean the coins, use the least harmful method. Very dirty or spotted coins can eventually corrode and become damaged. Again, use a professional service.

http://www.mycoincollecting.com/collecting/cleaning-coins.html

http://www.silversmithing.com/care.htm

Early methods of silver mining

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Mankind has mined silver for thousands of years. Two early methods of mining silver were sluicing and hard-wall extraction. Sluicing involves assembling trenches in irrigation holes to filter out heavy metals from the mine. Unfortunately, sluicing is inefficient and ineffective method for obtaining silver. Hard-wall extraction is a basic silver mining method that is still used today, although with greatly improved machinery.

In hard-wall extraction, drills and heavy machinery are used to get at the ore. While deposits of pure silver are still found, they are rare. More often, silver is found with other elements such as lead, zinc and copper buried deep in the earth. Once discovered, an underground mine must be dug and constructed. Large volumes of the ore are drilled and blasted. The ore is transferred to underground rock crushers. Crushed ore is then hoisted up to the surface or driven by truck via a spiral tunnel or decline ramp.

On the surface, the ore is crushed even finer and then ground. A flotation process separates silver-bearing galena from waste rock particles called tailings. The flotation process was developed in the 19th century and is still used today, with many improvements over time. The process involves mixing the ground-up ore, water and chemicals, which are then agitated in the flotation cells. When air is blown through the mixture in the cell, the silver galena rises while the tailings sink to the bottom of the cell. The resulting silver-lead sulfide concentrate is then melted to combine the particles into lumps, removing the sulfur as sulfur dioxide. The silver mixture is further refined by various methods until pure silver is obtained.

http://www.australianminesatlas.gov.au/education/fact_sheets/silver.jsp

http://www.precious-metal.net/silver/silver-mining/#ixzz1eYkq5Isu

http://www.madehow.com/Volume-3/Silver.html

Uses of silver in electronics

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Silver is widely used in electronics and is an integral component in making electronic goods. Name one electronic object in your house and you are likely to find silver in it. Let it be a microwave oven, toys, computer and computer accessories, televisions, telephones, the list is endless. Take a compact disc, you will evidently see silver there. So why is silver so important in all these things?

The major reason is because silver is a great conductor of electricity and is highly regarded for its ductility, malleability and strength. It is used in switches, conductors and fuses. The high thermal conductivity of silver is what makes it so popular. Because of its versatility, silver is in great demand in all industries, not just for electronic goods. The mechanical stability of silver is another reason for its great demand. When used in quartz batteries it will not just increase the working power of the cells but offers greater durability too. Using silver in electronic goods is highly cost-effective. Though gold is also a good conductor, silver is cheaper and that is why it is widely used. And it functions and lasts longer than any other known conductor of electricity. Silver has low polymer formation and that is another reason why it is extensively used.

Even if the silver gets tarnished a bit, it still conducts electricity remarkably well. It is believed that 40% of the overall silver ever produced goes into making electronic goods and that too in the US alone. After photography and silverware, it is in electronic goods that you observe the heavy use of silver.

Cannington Silver Mine

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Overview
The Cannington Silver Mine located in Quennsland Australia produces more silver and lead at lower cost than any other mine in the world. Owned by the mammoth public company, BHP Billiton, it employs close to 1,000 miners, staff and independent contractors.

History
In 1990, BHP Minerals was awed and more than a little elated by the massive find at Cannington. A$450 million and seven years later, the mine was opened and full production began in 1999. Capacity has steadily increased. Currently, on an annualized basis, three million metric tonnes of ore are processed yielding 750 tonnes of silver and 265 thousand tonnes of lead. In addition, substantial amounts of zinc are recovered.

Processing Methods
Currently, the Cannington mine produces six percent of the world’s silver and seven percent of its lead. To achieve these results, the ore is processed in a variety of ways. The first step is comminution, the simple mechanical crushing and grinding of the ore. The resulting material is then subjected to a variety of mechanical and chemical processes that concentrate the metals based on their physical properties. These properties range from density, particle size and shape, through electrical and magnetic properties, to surface properties.

Ultimately, the silver is leached from the zinc and lead streams in a separate chemical process. The separate metals are then smelted and stored for transportation. At Cannington, demand is so great that BHP Billiton maintains a railhead nearby for the storage and subsequent shipment of the refined metals.

Where the US stores silver

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The United States stores it’s silver supply in West Point, NY. The facility affiliated with the famed MS army military academy, is on the the same compound. West Point is located in upstate New York, near the city of Peekskill, New York. It was established as the United States Mint in March of 1988. It is also a landmark that is listed as a place or destination that has historical significance. This facility was once known as the West Point Bullion Depository. At one point, it hard the largest amount of Silver in the United States. The building itself, is a security steel concrete building, with a state of the security system in place. It is housed on a four acre of land, with the military academy on it’s immediate North side.

Around 1937, this facility did produce the coins that were circulated as part of the United States currency. It currently does not do that. It acts as a storage facility for the silver owned by the United States government. The facility has produced some historical coinage to signify historical events germane to the United States. Such as the coin that commemorated the Olympic Games that were held in Los Angeles in 1984. Today some coins are produced there to signify events having to do with the Military. The facility remains a private facility and is not open to the public for tours.