The unit of measurement used to measure the weight of a
stone in the jewelry world is the carat. The weight of the stone,
as well as its quality, are part of the precise criteria used to guide
the determination of its sale price in jewellery, and this in particular for
diamonds.

This weight is measured when weighing the diamond according to
a particular unit of mass specific to gems: the carat. Adopted in
1907 at the 4th General Conference on Weights and Measures, the metric carat
is equivalent to 200 thousandths of a gram, or 0.20 grams. In order to guarantee a
criterion of quality and absolute millimetric precision, the weighing is carried out
to the nearest hundredth or even thousandth. One carat is therefore divided into 100
dots; we thus speak of a “25 points” to designate a quarter of a carat, which
equals 50 milligrams, or 0.05 grams to weigh. In French, unity
is usually denoted "ct" for short, but in the world of
jewelry, we must not confuse the carat as we are talking about it, with that
which designates the purity of gold: "K" or "kt", for "karat"
in English. Thus, 1 carat equals 0.20 grams, and 0.1 carat equals 0.02
gram.

The tables below illustrate the correspondence between the diameter of a diamond
brilliant and its number of carats.

Visualize the relationship between diamond carats and diameters with these tables.

Table illustrating the millimetric correspondence of the diameter of a diamond and its weight
in carats.

Table illustrating the correspondence of the diameter of a diamond and its weight in carats.

The table below illustrates the evolution of the price of a diamond per carat, which follows an exponential curve.

Table illustrating the evolution of the price per carat.

The French word "carat" as such comes
etymologically from the Arabic word “kharoûb”, or carob in French. This designates,
the seeds of an African tree: carob seeds. According to the
historical research, these seeds have indeed long been used as
millimeter counterweights in the scales and thus served as a guide mass unit
to weigh the diamond. However, we must not confuse the carat which
determines the weight of the gems and which is commonly used in sale, and the
carat which determines the title of metals such as gold. Whether for
jewelry enthusiasts, jewelry lovers, or even for
future engagement planners, know the meaning of carat to you
will necessarily be useful in your search for the ideal diamond and the jewel of your
dreams, for a successful engagement.

The value and quality of gems are determined
by many criteria such as color (color), size (cut),
clarity (clarity) and weight (carat). These are the 4Cs, specified on the GIA certificate, and constitute
makes closely related guides related to determining jewelry value.
However, it is true that it is above all the weight of a stone that determines
exponentially its price. Large gemstones are rare, and provide
therefore a great value to the stone, even though a proportional relation
between mass and price is not officially established. It is thus vital
to carry out the most precise metric measurement during the sale, which will be
indicated on the GIA certificate, in order to correctly determine both the mass
(the carat) and the price of the stone and the jewel.

To measure the carat of a stone, it is necessary to use a special balance, in
taking some precautions. This scale will only be accurate if it is
protected from sources of heat, drafts or vibrations. Moreover,
Generally speaking, the weight of a gem depends on its shape. For example, a
2 mm round diamond weighs 0.03 carat, while a 2 x 2 mm square diamond
weighs 0.05 carats.

It is also to be known that this relation between the shape and the carat varies from one
stone to another: for example, a round sapphire 2 mm in diameter weighs
0.04 mm, while an emerald of the same size will weigh only 0.03 carat. That
is explained by the differences in density of each stone. Whatever
gemstone you choose, keep in mind that the larger the size is
larger, the more carats, the higher the price.

In addition, at equal weight, stones with high density will be smaller than stones
of a carat of lower density. Thus, for the same carat weight, the
sapphires will be smaller than diamonds because sapphire has a higher
density. On the other hand, a tourmaline weighing 5 carats may be larger
than what you had visualized, and that because tourmaline has a density enough
low. The weight / size ratio of a stone is thus directly linked to its
density. To illustrate, the density of ruby ​​is 3.97 to 4.05; that of
tanzanite is 3.35. Thus, the ruby ​​has a higher density and will be, at
equal weight, smaller than tanzanite.

Weighing of diamonds on a jeweler's scale (in grams).

When you look at a diamond, the first thing you can see is its size, its
geometric shape (round, oval, pear, heart, etc...). But its weight is not seen
not with the naked eye; it is its volume, its dimensions that we can see. He
so worth it in your search for the ideal stone to take
first take into account the visible criteria such as the dimensions of the stone,
its purity, its certificate… before looking at the carat.

Colorless diamonds or colored diamonds, precious stones or not, rubies, sapphires,
tanzanite… Whether for crimping rings, wedding bands, buckles
earrings, necklaces... On the occasion of an engagement or to enlarge your
jewelry collection… in any case, you will need to know what
one carat when purchasing a gem or piece of jewelry, such as for the acquisition of
rings or earrings.

In summary, during your search for the alliance, the rings or even the
ideal earrings, it is important to first focus on
visual criteria before looking at the carat: precious stones or
non-precious, colored or colorless, its dimensions… While
also interested in its purity and GIA certificate. Whether you are in
search for the ideal high-purity diamond for your future alliance or
simply to expand your collection, the choice of carat weight will come
afterwards, it's the final touch.