Inorganic Gemstones

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Gemstone Formation

There are various types of deposits and formations of gemstones (precious and semi-precious stones). The most important are as follows.

Magmatic Crystallization:
Magma, on cooling produce crystals of various minerals. Some of these, like diamond, are used as gemstone. Crystals formed at great depths may be brought to the surface by lava in volcanic eruptions. Minerals like moonstone, topaz and corundum are common gemstones of this type.

Pegmatite:
Towards the final stage of magmatic crystallisation, a thin silicate liquid remains and if this is squeezed into surrounding rocks, it produces pegmatites containing very large crystals. Many of these are used as gemstones. Tourmaline, topaz, beryl, quartz and spodumene are some of the common pegmatitic gem stones.

Hydrothermal vein deposits:
When most of the silicate matter in the magma has crystallized, what remains is a hot watery (hydrothermal) solution of various chemicals. These hot fluids penetrate the fissures and cracks in surrounding rocks and are precipitated in Veins. Examples are emerald, topaz, red beryl and benitoite.

Placer or Alluvial deposits:
Some minerals are highly resistant to weathering and when the rest of the rock has decomposed and disintegrated they are also carried away by flowing water. But because of their high specific gravity, they get deposited on the river bed giving rise to gem gravels such as those formed in Sri Lanka, Myanmar, India etc. Gemstones such as diamond, ruby, sapphire, chrysoberyl, zircon, garnet, quartz are commonly found in such deposits.

Chemical precipitates:
Chemicals carried in solution may be precipitated when the physicochemical environment changes. Common examples are malachite, opal, rhodochrosite and turquoise. E.g. when acidic copper bearing solutions move through porous volcanic rocks, they react with minerals containing aluminium and phosphorous to form turquoise.

Metamorphic deposits:
When a rock is subjected to high temperature and / or high pressure, the chemical components of its constituent minerals get rearranged into new minerals. Gem minerals formed in this fashion are diopside, corundum, andalusite, sillimanite, kyanite, epidote, garnet, iolite etc.


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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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