Friday, 22 February 2013

Precious metals in Crystal And Gems


EXCELLENT NUGGET This fine crystalline gold nugget, is known as the Latrobe nugget. It was found in 1855 in the presence of His Excellency C. J. Latrobe, the Governor of what was then the colony of Victoria, Australia. Large nuggets of gold are rare.
GOLD, SILVER, AND PLATINUM are crystalline, although single crystals are rarely found. Gold and silver were among the earliest metals worked, over 5,000 years ago. Platinum was first noted in 1735 as a white metal used by the Chibcha Indians of Colombia and today it is more valuable than gold and silver. All three metals are useful because they are relatively soft and easy to work. They are difficult to destroy and have high SGs.

Gold
CROWN OF PLATINUM The crown of Queen Elizabeth the Queen Mother is made of platinum. It is part of the British Crown Jewels.
Gold is used as a standard against which wealth is measured. Pure gold is a dense (SG=19.3) but soft (H=2.5-3) metal. Before it can be used, it has to be refined and for most uses it is alloyed with other metals to make it harder. Purity of gold for jewellery is measured in carats, pure gold being 24 carats.

Platinum

Platinum plays a key role in modern technology. It is used as a standard weight, for surgical instruments, and of course in jewellery. The name is derived from platina meaning little silver.


VALUABLE BONUS Silver is now mostly extracted as a byproduct from the mining of copper and lead-zinc deposits such as galena, a lead sulphide. These fine crystals of galena come from Silvermines, Co. Tipperary, Eire. Platinum is often found in granules, or small nuggets in placer deposits. There are major deposits in the USSR, Canada, and S. Africa but most are of very low concentration.

SILVER
Crystals of silver are rare, but cubic crystals are occasionally found. Silver usually occurs massive or as thick wiry aggregates. In medieval times, silver was more valuable than gold. It was the main metal used for money and was also used for fine metal-work having a hardness of only 2.5-3. Today, metallic silver is used in electronics, silver plating, and jewellery, and a huge amount is used in the photographic industry.

Writer –Dr.R.F. SYMES and Dr.R.R. HARDING



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