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Precious and Semi-Precious Stones

Updated on December 17, 2014
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Few Words About The History Of Precious and Semi-precious Stones

Human interest for precious and semiprecious stones is dating back to the Mesolithic Age. There is an evidence that ancient Greeks, Romans and Byzantines admired precious and semiprecious stones and held deep knowledge about them. The interest increased significantly with the growth of the trade during t 15th and 16th century.

The connection with astrology symbols, faith and supernatural forces also played a role and interest was maximised even more during the 18th and 19th century. Many new stones were discovered and introduced into market during those centuries.

How to Separate Precious from Semi-precious Stones

Stones (Gems) are divided into precious and semi-precious categories. Many gemstones including diamond, sapphire, ruby ​​and emerald are precious, while the semiprecious are amethyst, aquamarine, tourmaline, topaz, citron, tanzanite, garnet, zircon and many others.

Both categories of stones are divided into different types, varieties and groups. Stones with rare, unique colours are the hardest to find, which makes them more valuable in comparison with other gemstones of the same category. Precious and semiprecious stones are categorised according to the hardness, based on the scale of Mohs. Scale classifies minerals and divides them into the hardness from 1 to 10.

Scale of Mohs

HARDNESS
STONE
CHEMICAL FORMULA
1
Talc
(Mg3Si4O10 (OH)
2
Gypsus
(CaSO4.2H2O)
3
Calcite
(CaCO3)
4
Fluorite
(CaF2)
5
Apatite
(Ca5 (PO4) 3 (OH-, Cl-, F-))
6
Feldspar
(KAlSi3O8)
7
Quartz
(SiO2)
8
Topaz
(Al2SiO4 (OH-, F-) 2)
9
Corundum
(Al2O3)
10
Diamond
(C)

Colour

Colour is one of the most important characteristics of precious and semiprecious mineral stones. The colour of the stone used to be the only criterion for the recognition of precious stone. Some stones are immediately recognisable by their unique colour, while other stones, such as tourmaline which comes in different colours are difficult to identify.

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Transparency and Hardness of Gemstone

Transparency

This property is the ability to block the light that is passing through the stone. The transparency of the stone is affected by any inclusions; it might be contained with traces of other minerals, those inclusions can reach the size of grain.

The hardness of the stones is misunderstood, as many people believe that the hardness represents the resistance of the stone to any kind of pressure.

In fact it represents the resistance of the mineral stone to engravings. For example, the diamond is the hardest stone to be cut in comparison with other stones. There are many hardness scales out there but the most famous one is the scale of Mohs.

Precious Stones Cutting Techniques Through The Centuries

Bellow we can see how gemstones and particularly diamonds were cut over the centuries

1. Point Cut

2. Single Cut

3. Rose and Briolette Cut

4. Old Mine Cut

5. Old European Cut

6. Eight Cut and Swiss Cut

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Shapes of Diamonds and Gemstones

Round: The diamond that is shaped in Round form, is the most prevalent type of diamond cutting . It is also considered the best kind of shape that gives better shining attributes to diamonds. We all probably may have heard the term "ideal cut ". This term refers to the attempt of cutting a diamond into ideal proportions in order to achieve the maximum brilliance.

Emerald

Emerald Cut Diamond: Emerald cut diamonds have a rectangular shape with cut corners. This type of diamond is flat and each cut facet resembles large stair scales. Unlike the diamonds shape Marquise, here we do not have the phenomenon of refraction (bow-tie effect).

Caution : The best quality Emerald Cut Diamond must have the ideal colour.

Diamond Heart

Heart: The diamonds shaped as heart have a slight similarity with the diamonds shaped as Pear, except that there is an edge at the top of the gem. In fact, the reason to shape the diamond into heart or pear depends on the shape of original material.

Caution : The attractive shapes of the heart cut diamond must be equal and properly defined. The Heart, shape also carries the phenomenon of diffraction called (bow-tie effect).

Marquise Cut Diamond

Marquise

The name «Marquise» comes from the legend of the Marquis of Pompadour, it is said that the King Sun asked to cut a diamond into the shape of the mouth of Marquis.

Caution : Badly Marquise shaped diamond is often visible because of the phenomenon (bow-tie effect), even with the naked eye.

Oval Cut Diamond

The Oval shaped diamond resembles the round diamond with the exception that it is elliptical. It was created for the first time in early 1960s by Lazave Kariau. Usually this kind of cut has 56 facets . The attractive shape plays an important role in oval cut diamond.

Caution : The poor cutting of diamond is visible, due to phenomenon of (bow-tie), even with naked eye.

Pear Cut Diamond

The Pear shape diamond is a combination of Round and Marquise cutting. The pendants usually look very nice especially when the diamond is shaped as Pear. In the earrings because of their shape diamonds are resembling to tears.

Caution: Correct cut of a diamond is also visible because of the bow-tie effect

Princess Cut Diamond

The Princess cut is relatively new genre. It's a pretty attractive kind of cut. Several people prefer Princess Cut diamonds because they sparkle like Round Cut diamonds.

Caution: Pay attention on correct shape of diamond.

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    • Lady Guinevere profile image

      Debra Allen 2 years ago from West By God

      This was a very interesting article. Thanks for writing this up and sharing it with us. See you around hubpages.

    • MsDora profile image

      Dora Weithers 3 years ago from The Caribbean

      Thank you for the lesson on precious stones. It is great to learn about all these valuable items. Still love the diamond. Thank you.