Thursday, 30 October 2014

Gemology

Throughout the history, mankind has marveled at the beauty of gemstones. The charm of gemstones leaves one spell bound. They have been treasured for ages by maharajas, emperors and kings and have been passed on from one generation to another. If one has to define a gemstone, it can be said that a gemstone is a naturally occurring mineral with a distinct chemical composition wherein its atoms are arranged in a definite crystal structure.
GEMSTONES

*(A mineral can be defined as an inorganic natural substance)
There are certain exceptions to this definition like amber, pearl, coral, ivory, jet and ammolite. These are organic gems which have been bestowed upon us by nature, or in other words produced by a living organism or derived from a natural process. Another exception to this statement is a gemstone called – Opal, which does not have a definite crystal structure.



ORGANIC GEMS


Now, to have a better understanding of what can be termed as a gemstone one needs to know that most gemstones are minerals but all the minerals are not eligible to be called as gemstones. For a mineral to qualify as a gem it must have three characteristics- beauty, rarity and durability.

Beauty: Beauty can be defined as the overall appeal of the gemstone. It is determined by various factors like color, cut, clarity and phenomenon. These factors have a big impact on the pricing of the stones along with a few more factors.

Color: this factor is based on three important aspects- hue, tone and saturation. Hue is the first impression of the color or the light reflected back to the eye, tone refers to the lightness or darkness of the color and tone determines the strength of color. For gemstones like ruby, emerald and sapphire darker the color the better it is and vivid color saturations are preferred. On the other hand stones like aquamarine are known for their light hues. Showing an absolute contrast diamonds are colorless and this is the most important virtue which makes it breath taking.


HUE


TONE



SATURATION

Cut: cut can be defined as art of shaping the rough gemstones in precise angles and proportions to bring out the fire in them. The cut describes how a gemstone is fashioned and its shape. The more accurate and proportionate the cut, greater is the beauty of the stone. A stone can be either facetted or shaped into cabochons. A facetted stone is cut with flat symmetrical planes called facets and cabochons are cut to give a stone a smooth domed surface. There are different types of cuts for facetted stones and cabochons. Facetted stones can be fashioned with brilliant cut, step cut or mixed cut. The cut is chosen for a gem depending on what will bring out its beauty the best. For example a sapphire will be mostly cut as a facetted stone and gems like coral are usually fashioned as cabochons.
CUTTING STYLES


CABOCHON

Clarity: clarity of a gemstone is dependent on the presence of inclusions. An inclusion can be defined as a material trapped inside the stone or an internal stress fracture or growth marks. These inclusions have a great bearing on the transparency of a stone and hence on its beauty. In some stones inclusions add to the beauty of a stone, like star sapphires. But inclusions can also have a negative impact on the stone if it is very prominent.

INCLUSIONS

Phenomenon: many gems display optical phenomenon which not only add to their beauty but also make the gem very rare and unique. There is a variety of phenomena displayed by gems. For example moonstone displays the phenomenon of adularescence and opals display play of colors. Likewise there are other phenomena like chatoyancy, color change, aventurescence, asterism, iridescence etc. these optical characteristics of certain gemstones add to the overall appeal and beauty of the gemstone.

IRRIDESCENCE

ADULARESCENCE



ASTERISM

PLAY OF COLOR

Rarity: Rarity of a gemstone makes it highly desirable. Rarer the gem higher is the value commanded by it. Rarity of a gem is related to its formation process. For example certain gems like garnets are formed more commonly than rubies. Other factors which govern the rarity of a stone are a rare color in a species, like red beryl is a rare stone. Emeralds with no or few inclusions with vivid color are very rare. Similarly, cat’s eye alexandrite displays color change as well which is again very rare.

Durability: It can be defined as a vital virtue of a gem which allows it to pass from generations to generations. In other words durability is the ability of a gemstone to resist wear and tear. Durability of a stone is dependent upon its crystal structure. For example, the hardest known gem to mankind is diamond which belongs to cubic crystal structure which is highly symmetrical.

Gemstones have a special allure. They always manage to draw appreciation and admiration. They are not only objects of adornment but treasures which epitomise various shades of a human’s life. So add color to your life with gemstones!!





*The Author is a Colored Stone Graduate from Gemological Institute of America, Mumbai and a Diamond Graduate from Solitaire Diamond Institute, Bangalore. She also holds a Diploma in Jewelry Designing & Manufacturing from Jewelry Product Development Centre, Jaipur. She also blogs at 'The Jewel Affair'.

** Picture coutesy: Google Images