Coloured Gemstones
Wonders of nature
Coloured precious stones come in an incredible variety of colours, however, only few can be cut into gemstones. Rough crystals look like plain, dull pebbles; their true colours can only be guessed. Their colours, transparency and brilliance are only revealed once they are cut and faceted. The stonecutter’s job requires skill and years of experience.
Families of coloured gemstones
Coloured gemstones that have the same chemical and physical characteristics and which crystalize in the same system are combined into family groups. For example, ruby and sapphire are mineralogically the same, differing only in their colours; they belong to the family of corundums. Emerald and aquamarine belong to the family of beryls.
Colour & purity
Element colouring
In terms of pure chemical composition, most coloured gemstones would be colourless. They obtain their colours by their content of a small quantity of trace elements. Sapphires obtain their colours through iron and titan, rubies and emeralds through chrome.
Purity
Above all, colour and purity determine the value of a stone. A gemmologist judges every stone according to its primary colour, uniformity and the intensity of its colour. The fewer inclusions a stone has, the more valuable it is. However, inclusions can also be interesting: very often they confirm the authenticity and the origin of the stone.
Deposits
Coloured gemstones grew millions of years ago inside the Earth under tremendous pressure and extreme temperatures. Deposits are found almost all over the world, however, certain families of gemstones are limited to certain areas. A good example is the former Gondwana continent, which extended from Madagascar to the Himalaya, where we find the same corundum and spinel families.
Mining
Primary and secondary mining
Primary mining refers to gemstones that are mined at the place where they grew. Secondary mining is when rough crystals are transported from their original place through erosion into rivers and are eventually deposited in riverbanks and terraces.
Profession & passion
In 1970, Thomas Frieden started a wholesale business with precious gemstones and cultured pearls, adding two important pillars to the existing business activities of the jewellery manufacturer. Thomas Frieden combines passion and business: his regular trips to mines and marketplaces created an extraordinary worldwide network and a steady stream of market information, such as availabilities, prices and trends.
Expertise & market knowledge
Thanks to regular trips to mines and marketplaces, Thomas Frieden created an extraordinary worldwide network and receives a steady stream of market information, such as availabilities, prices and trends. Frieden’s profession is discovering exclusive coloured gemstones for its own workshops or for the wholesale business. Discovering absolute rarities is a passion that often requires strenuous trips to mines in remote areas.