Everything you need to know about diamonds

What is a diamond made of?

The physical characteristics of diamond

Composition of a diamond

A rough diamond is composed of pure carbon (C), it forms at very high temperature and pressure in the crust of the Earth's mantle.

Although it is composed of carbon atoms, rough diamond can however contain other substances such as boron (B), nitrogen (N), inclusions of graphite, aluminum (Al), silicon (Si), calcium (Ca), magnesium (Mg), iron (Fe), etc.

These substances are sometimes solid, they are recognized by the presence of visible inclusions in the diamond; these impurities are sometimes invisible and are causes of the color of the diamond. Boron (B) for example can give the blue color of a diamond.

Structure of a diamond

Diamonds are gemstones that have a cubic crystal structure and take the shape of an octahedron when found in nature. This is because when they are composed, the carbon atoms (C) are arranged in such a way that they form a cube (see the diamond-like lattice below).

The hardness of diamond

In order to characterize the hardness of a gemstone, the mineralogist Friedrich Mohs invented, in 1812, a scale allowing us to measure the hardness of minerals. The Mohs scale starts at 1, the softest mineral (talc), and ends at 10, the hardest mineral (diamond). Diamond is therefore the most resistant natural material in the world. However, it remains fragile; if it is struck precisely on one of these cleavage planes, it would split into several parts.

Other characteristics of diamond: refraction, density, thermal and electrical conductivity and coloration

In addition, diamond turns out to be an excellent thermal conductor, with a particularly high refractive index (2.4), giving it incredible dispersion of light.

Colorless or white diamonds are the best known. As mentioned above, imperfections can give color to diamonds: yellow, blue, blue-gray, black, red, green, pink, etc.

Natural diamond can be transparent, translucent or opaque. Some diamonds fluoresce blue under ultraviolet light.

Where can you find diamonds?

Diamond producing countries

Diamonds are mainly produced in the following countries: Russia (Udachaya kimberlite mine), Canada (Ekati kimberlite mine), Botswana (Orapa mine) and South Africa (Finch mine).

Extraction and trade

Diamonds are mined from three different types of deposits: primary deposits (in open-pit or underground mines), secondary alluvial deposits and coastal marine deposits.

Primary diamond deposits

Diamonds are formed in the Earth's crust, about 150 kilometers deep, in conditions of extreme pressure (50 kbar) and temperatures (1100°C). These gems are surrounded by a magma called "kimberlite magma". The latter follows "currents" in our Earth's mantle and sometimes initiates movements towards the surface, which can accelerate. The violent speed of this movement carries and tears away the gems and rocks in its path through a chimney (pipe) thus carrying the diamonds to us. Several volcanic eruptions can use the same chimney. We know, for example, that the Premier mine in South Africa has experienced 15 eruptions.

Diamonds from these primary deposits are mined in open pits (sometimes underground). The chimney is dug and blasted as it goes along to find diamonds stuck in the surrounding rock. Thus, steps run along the chimney and form concentric circles through which trucks pass in order to extract the rocks in debris. These rocks are then processed and sieved to find the diamonds.

When diamonds are mined, they are sorted and graded according to their quality and size. Larger and better quality diamonds are the most sought after, and will therefore fetch higher prices. Once the diamonds are sorted and graded, they are sent to diamond exchanges, where they are bought and sold by traders around the world.

Secondary diamond deposits

After being expelled by a chimney, the diamond can sometimes continue its journey thanks to the natural erosion of the volcano by the weather. Diamonds can be transported and stop in "alluvial" deposits, sometimes in the bed of a river or in the seabed. This concerns for example Namibia, where the seabeds are searched by a mechanized system and where the equivalent of 500,000 carats of diamonds are recovered per year.

What does the word "carat" mean?

The word "carat" is a term that is used to determine the weight of a diamond. One carat equals 0.2 grams and is used to compare its weight to other diamonds of the same size (the way it was cut). The heavier a diamond is, the rarer it is, and therefore the more expensive it is.

How are diamonds priced?

Diamond prices are determined based on specific evaluation criteria called the "4Cs": color ( Color ), mass ( Carat ), clarity ( Clarity ) and cut ( Cut ).

Color: A white diamond is a colorless diamond that is assessed according to these terms: exceptional white (absence of color), extra white, white, nuanced white, slightly tinted, tinted, yellow.

Totally yellow diamonds are considered colored diamonds and are measured by a different color scale.

Carat: A carat is a unit of measurement for the weight of a diamond. A 1 carat diamond is a diamond weighing 0.2 grams. Only diamonds over 0.50 carats are considered rare.

Clarity: A diamond is graded according to its degree of clarity visible under a 10x loupe or with the naked eye, ranging from "flawless", through a very small visible inclusion (VVS: very very small inclusion); a small visible inclusion (VS: very small inclusion); small visible inclusion (SI: small inclusion), visible inclusion (I: inclusion).

Cut: the cut of a diamond is assessed by the way it is cut in order to obtain the maximum fire (play of light in the diamond) from the gem. The proportions of the cut parts of the diamond are evaluated. Old cut diamonds, for example, reflect less play of light than brilliant cut diamonds, which is why old cut diamonds are significantly less expensive.

So, according to these quality criteria, the heavier, totally colorless, inclusion-free and brilliant-cut a diamond is, the more expensive it is.

How to get a diamond appraised?

Diamonds are often inherited or given as gifts, either for a wedding or another occasion. It is difficult for the lucky recipient to know the real value of this precious stone. Evaluating a diamond is a real profession. You must be a gemologist to evaluate the four criteria mentioned above, to have a certificate made by a gemological laboratory and to know the intrinsic value of your diamond.

Having a certificate issued by a recognized independent laboratory is interesting for several reasons:

- in case of theft: the certificate can be received by the insurance
- in case of sale: the certificate is the identity card which highlights the qualities of your diamond

If you have a diamond that you would like to have appraised because of its large size (over 0.80 carat approximately), do not hesitate to contact us. Maison Mohs has its own expert gemologist on site. We can, as a first step, give you an estimated price range. Then, following the production of a certificate of authenticity (one week for its production with an independent laboratory) corresponding to the identity card of the diamond (color, weight, purity and size) we can refine its potential sale price and give you the information you need.

If you have diamond jewelry, this concerns the current estimates and appraisals that we can carry out on site in our Parisian offices. We will thus be able to inform you of the average price of your diamond-set jewelry.

All our jewelry with diamonds .