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Gemstone Carat Weight: Tavernier's Law

Carat weight is an important factor in determining a gemstone's value, as larger stones are generally more valuable due to their relative rarity. However, other qualities like color and clarity also influence price. The carat unit of weight originates from the seeds of carob trees. Today, one carat equals 0.2 grams. While price per carat tends to increase with weight according to Tavernier's Law, many other factors complicate pricing, especially for colored gemstones where large stones may have flaws making them less valuable. Size and weight are different, as the same volume can have varying mass depending on the specific gravity of the material.

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182 views2 pages

Gemstone Carat Weight: Tavernier's Law

Carat weight is an important factor in determining a gemstone's value, as larger stones are generally more valuable due to their relative rarity. However, other qualities like color and clarity also influence price. The carat unit of weight originates from the seeds of carob trees. Today, one carat equals 0.2 grams. While price per carat tends to increase with weight according to Tavernier's Law, many other factors complicate pricing, especially for colored gemstones where large stones may have flaws making them less valuable. Size and weight are different, as the same volume can have varying mass depending on the specific gravity of the material.

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xem lo hang
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© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Gemstone Carat Weight

Carat Weight is an important quality of gemstone value. Often the larger the stone, the more
valuable it is, as larger stones are less common. However, it is important to remember that
qualities such as color and saturation are also important in determining a stone's value.

The English word carat comes from the


Greek word for keration ('little horn'), Gemstone Carat Weight Scale
referring to the shape of the seedpods of
the carob tree. These seeds are small and uniform in weight; therefore, they were a standard for
weighing gemstones in early times.

Around 1920, the metric carat was adopted as an international standard. One carat equals a fifth
of a gram (0.20 grams), so there are five carats to the gram.

Tavernier's Law
Generally, as a gemstone's carat weight increases, so does the price per carat. A fun way to look
at stone value is the following: Since the late 14th century there has been a law for diamonds that
is known as the 'Indian Law' or 'Tavernier's Law':

   Wt² x C = Price per stone

The following shows how the price of a diamond might increase with this formula applied to a
$1000 a carat base price.
Weight     Total Stone Price    
1ct $1000
2ct $4000
3ct $9000
4ct $16,000
5ct $25,000
10ct $100,000

However, in the real world, pricing is not this simple, even for diamonds. Other qualities such as
color or clarity will also greatly affect the price of gemstones. With colored gemstones, this carat
law is even more muddled and unrealistic. For example, a high quality ruby of three carats may
be more valuable and rarer than a ruby of over 200 carats, as huge rubies are common, but full of
serious inclusions. These giant specimens are impossible to cut into fine stones because of their
flaws; therefore, their value is very low.

Also, remember that size and weight are different. Size refers to the physical space or volume
that a stone occupies, while weight refers to the gravitational pull of the object. For example,
one cubic millimeter of sapphire will be twice as heavy as one cubic millimeter of opal because
the sapphire's specific gravity is twice that of opal. Please see our page on calibrated sizes for
more information.

 First Published: September-21-2006


 Last Updated: September-22-2016
 © 2005-2018 GemSelect.com all rights reserved.
Reproduction (text or graphics) without the express written consent of GemSelect.com
(SETT Company Ltd.) is strictly prohibited.

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