Inorganic Gemstones

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Mining

The methods used in the mining of gem materials are many, from native mining to highly technical methods.

  • Open Cast Mining:
    It includes the removal of overlying minerals or rocks to reach the gem bearing rocks. The gem - bearing rocks are then washed by jets of water under high pressure or by traditional methods to obtain the gem gravels. These gravels are then washed and assorted at the treatment plants. Opencast mining is done in many parts of the world e.g. Myanmar, Sri Lanka, U.S.A., Brazil etc.
    • Pit mining is the term used to describe a mining method where pits are dig up to about 12 meters. Open cast mining operations are generally initiated by pit mining.
    • Terrace mining is the term used to describe a mining method where the gem bearing rocks are exposed by digging horizontal terraces in step-like, generally circular formations. Blasting or digging is done and the debris is then washed to obtain the gem gravels. Emerald mining in Columbia (Chivor Mine) is the best example of terrace mining.
  • Underground Mining:
    This includes mining from alluvial and pipe deposits. In the case of alluvial deposits where pit mining is done, deeper pits of over 10 metres are considered by some as a form of underground mining.
    • Tunneling technique is employed when there is a gem - bearing rock either as an outcrop or as a seam running close to the surface. A tunnel is made from the surface to the gem - bearing rock and mining is done by blasting or by using pick axes to remove individual gem rough. This type of mining is seen at a few emerald mines in Columbia.
    • In Block caving, a series of parallel tunnels called scraper drifts are driven from the main shaft into the pipe, about 400 to 600 feet below the top of the mother rock. Starting at the top level, whole blocks of blue ground are mined out by blasting of the roof of the tunnels through conical draw points into the scraper drift. This is then transported to the main shaft and then to the surface.
    • In Chambering, initially a main vertical shaft is sunk into the rock surrounding the pipe. tunnels are driven into the pipe from the main shaft at established levels of 600, 1000 and 1600 feet. The ore is retrieved by blasting and transported to the main shaft and then to the surface. Levels are worked on, till a seam is exhausted.

Block caving and chambering are commonly used in diamond mining where the deposit is a pipe deposit. In general, block caving techniques are almost completely mechanized; all operations are carried out in one level only. This gives better yields and higher levels of safety and efficiency, as against chambering techniques.

  • River Diggings:
    Gemstones which have been deposited in river and lake beds can be mined by this method.
    • Dry Diggings: In this type of mining, a river has either changed its course naturally or is made to change. This is done artificially by blocking the river at two ends and creating a canal to divert the water. In whichever manner, the rock bed is allowed to dry and then the gravel is sieved to obtain the gem rough.
    • Wet Diggings: In such diggings the gravel is removed from the flowing river and then sieved to separate the gem rough.
  • Sea:
    • Undersea or Marine Mining: This type of mining is used wherever there are marine deposits. These may be on the beach, as in the Namaqualand diamond deposits in West Africa, or they may be off - shore deposits. This type of mining may involve land reclamation or even deep sea dredging. Mention must be made of the organic gem materials and the manner in which they are retrieved. Amber and Jet are recovered by pit mining while amber is also fished out of the waters, as is seen in the Baltic Sea. Corals are collected by divers with specialized equipment to remove and cart them out. Pearls are recovered by divers who collect the pearl bearing molluscs from the sea bed.

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Jewellery is one of the most bought products online. An estimated $1 billion USD of diamonds are bought annually via the Internet. Over 40 million people use the Internet to trade!

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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