4: Precious stones

Gemmology is the science dealing with the characteristics, authenticity and value of gemstones. According to current gemmological classification in Finland, precious stones comprise only the 13 minerals, from diamond to opal. The most famous precious stones, in addition to diamonds, are rubies, sapphires, emerald and topaz. Opal and tourmaline are considered the most colourful precious stones, as they can be found in virtually any colour.

Diamond

Most mined diamonds are yellowish, brownish or clear. The rarest and most valuable diamond colour is red. The colours are caused by impurities, meaning that diamonds can contain trace amounts of other materials. The most common impurity is nitrogen, responsible for the yellow colour in diamonds. Boron, on the other hand, causes the colour in blue diamonds, and hydrogen or nickel in violet ones. In addition to colour, the value of a diamond is impacted by its weight in carats, clarity as well as the cut, including the polishing that brings it its famous shine.

Diamonds have been found all over the world, generally in old bedrock areas. They have been found in Finland as well.

Koh-i-Noor, considered the world’s most valuable precious stone, is also a diamond. It has no clearly estimated value or known origin, but it may have been discovered in India as early as around a thousand years ago. Since then, the ownership has transferred from India to Iran, back to India and then to the Great Britain, where it is part of the Crown Jewels of the United Kingdom. Koh-i-Noor is currently set in the Queen Mother’s Crown, together with around 2,800 other diamonds.

Corundums

A pinkish orange variety of sapphire is called padparadscha. The most cherished rubies are pigeon blood red, and the most expensive sapphires cornflower blue. Sometimes corundum has been heat treated to improve its colour. A temperature of around a thousand degrees Celsius will lighten blue colours, whereas heating the stone to 1,000–2,000 degrees Celsius can intensify its colour and improve its clarity.

Sapphires have been cherished throughout history and used for different purposes, including religious rituals. Princess Diana’s engagement ring has a 12-carat sapphire. Prince William later gave the same ring to Kate Middleton. Corundum has been found in the Alps and Greece, among other European locations. The majority of the world’s best corundum has been found in Burma (Myanmar), Sri Lanka, South Africa, Madagascar and Australia.

Beryls

Other varieties of beryls often contain other elements as impurities: chromium turns beryl into brilliant green emerald, whereas iron colours it deep blue, called aquamarine. The pink beryl, called morganite, owes its colour to manganese, and Fe3+ ions (iron) produces the golden-yellow colour of golden beryl. The most valuable beryls are emeralds with a vibrant green colour and a slight blue hue.

The first known emerald mines resided in Egypt. The Egyptian ruler Cleopatra was a known gemstone collector. Emeralds were her favourite, and she shared them as tokens of gratitude with her most loyal servants and as presents with her partners. During the periods of Ancient Egypt and later the Roman Empire, it was believed that emeralds could strengthen sight and cure eye diseases as well as encourage rebirth. For this reason, rulers and other important people were buried with them. The world’s most expensive polished emerald, Rockefeller, was found in Colombia, as were many of the most cherished deep-green emeralds. It weighs 18 carats and was sold for around 6 million euros. The largest uncut gem-quality emerald (raw emerald) was found in Zambia in 2021. It weighs an astonishing 1,505 kilograms. It is called Chipembele, meaning “rhino”.

Topaz

Colour variation in most other precious stones is caused by trace amounts of impurities, such as metals. As for topaz, the colour changes into yellow or blue in a different way. Sometimes the crystal structure of topaz contains either a gap or an extra electron. These anomalies in the crystal can absorb some of the wavelengths of the light shining into it, changing the colour of the light coming out, usually to yellow or blue.

The most valuable topazes are now found in Brazil. There have also been notable topaz mines in Germany, Australia and the Ural. Finnish topaz has been discovered in various locations, such as Eurajoki, the most famous deposit being in Viitaniemi, Orivesi, where topaz has been found at least in blue and yellow shades.

Up until around 200 years ago, topaz was indistinguishable from olivine or its gem-quality form peridot due to the colour variation. Presumably, real topaz was never discovered on Topazios, but the discovered stones were all peridots.

Amber

The Baltic region near Finland is home to the most famous amber deposit: it has been found in abundance on the shores of the Baltic Sea, from Estonia to Poland and Denmark. Finland has some deposits in the coastal areas, at least Pargas, Ingå and Nagu. They are thought to have been carried there by water. The Baltic amber has been estimated to be around 30–50 million years old. The world’s oldest amber finds are at least 320 million years old. Amber has been used in jewellery for at least 12,000 years. It has always been a valuable, luxurious gemstone for the wealthy. Real amber can be distinguished from a counterfeit by its weight: amber sinks in water but floats on salt water (seawater).