Citrine is a variety of the mineral Quartz. It has a pale yellow to brown color. Its hardness is 7 on the Mohs scale, similar to that of emerald.
The main deposits are in Brazil, Madagascar and the former Soviet Union.

Topaz is an aluminum nesosilicate. In its purest form, this stone is colorless. Other elements turn it light blue or golden brown to yellow orange or pink to red.

Topaz is often heated or irradiated to produce a deep blue, orange, light blue, pink or purple color.

It is one of the hardest natural minerals, with a hardness of 8 on the Mohs scale. It is between that of sapphire and emerald in terms of hardness. Topaz can break fairly easily along its fracture lines, though, so it should be treated with caution.

Topaz is mined on every continent. Brazil is the main producer.

Amethyst is a form of mineral quartz. Its color ranges from light to dark purple.

Amethyst's hardness is 7, similar to emerald and tourmaline. Prolonged exposure to the sun can cause the color to fade.

Amethyst occurs worldwide. The main extraction sites are in Brazil,

Until the seventeenth century, it was among the most valuable gemstones along with diamond, ruby emerald and sapphire. After the discovery of large deposits, however, its value dropped. Amethyst today is counted among semi-precious stones.

Sapphire, like diamond, ruby and emerald, is counted among the precious stones. Like ruby, it is a crystallized form of the mineral corundum. It is the third hardest mineral in the world (after diamond and moissanite) with hardness 9 on the Mohs scale (Diamond is 10).

Sapphire is best known for its blue color, but there are also beautiful yellow, purple, orange and green sapphires.

The highest quality stones are found in Kashmir. In addition, sapphires from Myanmar (Burma), Sri Lanka (Ceylon), Thailand (Siam) and Madagascar are also of excellent quality.

Like diamond, sapphire and emerald, rubies are traditionally counted among gemstones. Ruby, like sapphire, is a crystallized form of the mineral corundum. Unlike sapphire, a ruby is always red to pink. Sometimes a pink ruby can also be called pink sapphire. The distinction between these is subjective.

Ruby is one of the hardest materials found in nature and has hardness 9 on the Mohs scale. This makes it very hard-wearing and therefore very suitable for daily wear as jewelry.

The value of ruby depends on its size (carat), color and purity. The most valuable color is "pigeon's blood. Stones with few visible impurities are more valuable, but rubies without inclusions are often extra treated or synthetic.

Almost every ruby is heated before being cut. This improves the color but does not diminish the value.

Rubies are mined on every continent. The main deposits are Kashmir, Myanmar, Thailand and Cambodia.

Emerald is part of the gemstones along with diamond, sapphire and ruby. Emerald is a crystallized form of beril. Emerald is always medium to dark green, with yellow or blue as a secondary hue.

Emerald is relatively hard, with a hardness of 7.5-8 on the Mohs scale, but is rather fragile and brittle. Emerald is therefore not recommended as a stone in a ring or bracelet worn every day.

The value of emerald is determined by its size and especially its color. The more intense the color, the more expensive. An emerald always contains visible impurities. These inclusions are proof of authenticity.

Almost all emeralds are treated with oil. This on the cracks and fracture lines to fill and improve strength. Untreated emerald is rare and is therefore much more valuable than treated stones.

Emerald is found all over the world. The main mining sites are in Colombia and Zambia.

Tourmaline is a cyclosilicate mineral. Its hardness ranges from 7-7.5 on the Mohs scale, making it slightly softer than emerald. Tourmaline comes in different varieties and colors:

Achroite: Nearly colorless

Rubellite: Pink - Red

Dravite: Yellow-brown to dark brown

Verdelite: Green

Indigolite: Blue

Siberite: Lilar red to violet blue

Schorl: Black

Sometimes two to three different colors occur in a single stone. A well-known example of this is "Watermelon": red with a green rim.

The value of tourmaline varies significantly by type, size and color. the Paraiba, a blue and green variety, from a very limited area in Brazil is more valuable than diamonds.

Most tourmalines are mined in Brazil. They are also mined in Africa and Asia.