Inorganic Gemstones

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Extraction Techniques

Extraction of Rough Gemstones from the Ores

The process of extracting the gemstones from the ores varies from place to place and is dependent on the nature and quality of the gemstone. In general those from alluvial deposits are assorted by washing with sieves.

  • Slurry containing the gemstone rough along with mud and other materials is washed with water on a sieve. A vibratory motion is applied to the sieve so as to separate the slurry quicker. The gem rough is then hand picked from the sieves. Depending on the size of the rough, different sieve sizes are employed. This method is commonly employed for most gemstones.

Extraction of Rough Diamonds from the Ores

In the case of Diamond extraction from the mother rock, the process is more complicated. The entire process however utilises the properties of diamonds to separate them. Following are the basic processes by which diamonds are recovered from the ore.

  1. Crushing: Done to reduce the size of the rocks in the ore.
  2. Heavy Media Separators: Make use of the property of specific gravity wherein a heavy stone will sink in a liquid of lower specific gravity. Either one or a series of Heavy Media Separators are used to separate the diamonds. A centrifugal force is applied to the liquid inside, for faster separation.
  3. Grease Table or Belt: Uses the property that diamonds stick to grease. The ore is poured over this table and washed with water. A vibratory motion is given to the table. The diamonds with a few other minerals stick to the table while the rest is washed off. Heat is used to separate the diamonds from the grease.
  4. X - Ray Separators: Uses the principle that diamonds fluoresce to X - rays. The ore is dropped in a fine stream through a channel and an X- ray beam is directed at it. As a diamond fluoresces, a detector activates an airjet and the diamond is directed into another channel.
  5. Magnetic Separators: In areas where there are magnetic minerals present in the ore, a magnetic belt is used for separation.

The material which is discarded, also known as tailings, after going through the processes in a treatment plant is sometimes re-checked and is considered in the evaluation of the efficiency of the plant. The diamonds which have been separated are now washed in acid and cleaned, ready for assortment. Diamonds which are coated will probably not react well to the above processes. Under the circumstances, the quality of the rough should be ascertained before the specific processes are employed.

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In Germany, the garland of ambers is hung around the necks of the infants, so that their teeth might come out without much trouble.

In Turkey, people fix a piece of amber in the hubble-bubble, dogged by an age old belief that the presence of the jewel would destroy all the germs and no disease would spread, even after many have dragged their puffs from it.

In Greece, people think if wine is poured into the cups made of amethyst, one does not get drunk after drinking that.

In Rome, a talisman having coral pieces is considered very auspicious to quell the bad spells of evil look. The Romans were in the habit of hanging chains made of ancient coral pieces from the cradle of the infants to protect them from evil effects.

In China, people wear rings studded with tiny conch or oyster shells as they believe it cures all aches such as stomach ache, worms and like.

In India, pendants made of silver and studded with pearls are hung from the necks of the children to save them from any bad effects.

Greeks still believe, if women wear blue sapphires then no sense of immorality would pollute their mind nor can any fear of the supernatural can trouble them.

The Pope Innocent III had circulated an order asking all the priests wear blue sapphire, so that morality can be strengthened.

It is said about turquoise, that when the stone changes its color into yellow, it actually signals bad times to the person who wears it.

It is believed that a turquoise gifted to a friend or a lover turns his or her life into one of happiness and good luck.

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