Ruby

Ruby belongs to the corundum family, of which it is the red variety (the other variety being sapphire).

Its red hue comes from the chromium oxide that the ruby ​​contains.

Ruby has a hardness slightly lower than that of diamond: 9 against 10 for the diamond on the Mohs scale.

There are several shades of red, the one called "pigeon blood" is the most expensive.

Ruby is rarer than diamond. With equal weight, for rubies over 3 carats it is not rare that the price of a "pigeon blood" surpasses that of a diamond of high quality and the same weight.

Sapphire

Sapphire is another precious stone from the corundum family. Sapphire has a hue ranging from light blue to dark blue. Its color is due to iron and titanium often unevenly distributed on the stone.

Sapphire, without any adjective, is always blue but there are also green sapphires, yellow sapphires, ... and very rarely colorless sapphires said "leuco-sapphire" or orange sapphires also called "padparadscha".

The hardness of the sapphire is not homogeneous and varies according to the directions which makes its size particularly delicate.

Sapphire is a gemstone much more common than ruby, iron being much more prevalent on earth than chromium oxide.

Sapphire is the least expensive stone of 4 precious stones especially for weights less than 15 carats.

Emerald

Green in color, this gemstone has uneven transparency except for very high quality stones. The emerald's vitreous luster takes its color from chromium and vanadium.

Emerald owes its name to the Greek "smaragdos" (green stone) which later became emerald. It is by far the most popular stone of the Beryl family. The transparency of the stone is uneven and it is manifested in the stones of first quality, its brightness is glassy. Chromium and vanadium are the coloring substances of this prcious stone. In intense green color, it is very sought after. Light green color is synonymous with low quality.

The emerald is relatively fragile and it must be avoided shocks and put in contact with chemicals that can alter it.