DIAMOND

Brilliant (from the French brillant “brilliant, sparkling”) is a diamond that has been cut into a faceted shape through processing, bringing out its natural brilliance as much as possible. Diamonds are graded according to the "4 C" system: cut (cut), clarity (clarity), color (color) and carat (mass in carats), which allows you to determine how close the stone is to perfection. Not every faceted diamond is a diamond - only one that has a brilliant cut. The main thing in assessing the cut of a stone is its quality: how geometrically accurate and proportional the edges are. The ideal cut is encoded with the letter "A", then - B, C, D - in descending order of quality. In the international system (GIA), the ideal cut is designated as Excellent, and in descending order of quality (Very Good, Good, Fair, Bad). [Source not specified 1530 days]

Clarity is the most [source not specified 1530 days] significant indicator of the quality of diamonds: it is expressed in the presence or absence of stone defects or foreign inclusions; a diamond without flaws is called a pure diamond.

The mass of diamonds is measured in carats: 1 carat is equal to 0.2 grams.

Most diamonds are fluorescent, the ability to glow when exposed to ultraviolet light.

Diamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. At room temperature and pressure, another solid form of carbon known as graphite is the chemically stable form of carbon, but diamond converts to it extremely slowly. Diamond has the highest hardness and thermal conductivity of any natural material, properties that are used in major industrial applications such as cutting and polishing tools. They are also the reason that diamond anvil cells can subject materials to pressures found deep in the Earth.

Because the arrangement of atoms in diamond is extremely rigid, few types of impurity can contaminate it (two exceptions are boron and nitrogen). Small numbers of defects or impurities (about one per million of lattice atoms) color diamond blue (boron), yellow (nitrogen), brown (defects), green (radiation exposure), purple, pink, orange, or red. Diamond also has a very high refractive index and a relatively high optical dispersion.

Most natural diamonds have ages between 1 billion and 3.5 billion years. Most were formed at depths between 150 and 250 kilometres (93 and 155 mi) in the Earth's mantle, although a few have come from as deep as 800 kilometres (500 mi). Under high pressure and temperature, carbon-containing fluids dissolved various minerals and replaced them with diamonds. Much more recently (hundreds to tens of million years ago), they were carried to the surface in volcanic eruptions and deposited in igneous rocks known as kimberlites and lamproites.

Synthetic diamonds can be grown from high-purity carbon under high pressures and temperatures or from hydrocarbon gases by chemical vapor deposition (CVD). Imitation diamonds can also be made out of materials such as cubic zirconia and silicon carbide. Natural, synthetic and imitation diamonds are most commonly distinguished using optical techniques or thermal conductivity measurements.