Gemstone Glossary

The Earth gives up its most magnificent treasures when we unearth gemstones

Everlasting diamonds, blood-red rubies, the deepest green emeralds and dark blue sapphires. Aquamarines in all the colours of the ocean, purplish violet amethyst, golden yellow citrine, tourmaline in every colour of the spectrum, luminescent blue violet tanzanite, cognac-coloured topaz and many more. Shiny, lustrous pearls from water and rivers. We would like to introduce you to the special features of the most familiar precious stones and inform you about the various ways they can be enhanced.


The name aquamarine is derived from the Latin word for “seawater” which conjures up an image of beautifully pure and clear blue water. It is very closely related to the emerald, however, unlike the emerald, large specimens of aquamarine are often found which have exceptional clarity. Aquamarine varies in colour from pale light blue through to intense dark blue. The stones are gently heated for hundreds of years which creates these beautiful colours. Natural aquamarine derived from nature tends to be a greenish blue. Light green and yellowish stones are called beryl, so mineralogically speaking aquamarine is blue beryl and emerald is green beryl.



The most well-known and valuable gemstone of the large quartz groups are the purple-coloured amethyst and the yellow to red-brown citrine. They score 7 on the hardness scale. The Greek word amethystos means “not drunk” and it said that the name is derived from the fact that the stone is like the colour of wine, although it was formerly violet in colour. Pliny the Elder wrote about the magical powers that were attributed to the amethyst. Colour changes which take place through heating or burning to create citrine-coloured burnt amethysts can only be seen in stones found in specific sites. The intensity of the colour perhaps corresponds with the stone’s previous violet colour. Green quartzes are called prasiolite. Spectral analysis has shown that potassium ferrocyanide and ferric thiocyanate are responsible for giving amethyst its colour. These stones are found in Brazil, Sri Lanka, Mexico, Russia, South Africa, Tanzania and Uruguay.


Chrysoberyl are truly beautiful. Unfortunately, they are not so well-known, but they are very colourful and durable precious stones. Their most common colours vary from pale yellow to greenish yellow and from golden yellow to golden brown. The most precious variety called alexandrite can play an unusual magic trick: it changes from green in daylight to red in artificial light! Under a spotlight it is possible to see a curved bright line of light in certain cabochon-cut chrysoberyl stones which is why these types of rare and precious gemstones are called chrysoberyl cat’s eye.


The hardest natural material on Earth has been a particularly special source of fascination for humans for thousands of years. The diamond’s timeless quality has made it the symbol of constancy, devotion and love. A perfectly cut diamond has incomparable brilliance, vibrancy and sparkle. A brilliant cut diamond has 58 facets. The most valuable diamonds are completely colourless and do not have any imperfections inside the stone. Natural inclusions depreciate the stones, however, this also shows that the diamond is authentic, almost like a natural certificate of authenticity! Inclusions and fissures can be removed using technical and chemical processes, however, they are not always durable, and it is vital that this is clearly explained to you because diamonds that have been treated in this way have a much lower value. Completely colourless diamonds or diamonds with intense natural colours from yellow and brown to pink and blue are extremely rare and therefore command the highest prices. The colour of a diamond can actually be changed artificially using irradiation and heat. These are usually yellow, blue or more rarely pink and are much cheaper which is why it is critical that you know this when you purchase them.


Most of us are familiar with unmistakeable rosette-shaped clusters of small dark red garnets. Garnet is actually the family name of a large number of precious minerals. Some of these precious stones are highly sought-after and look very different to each other. The most familiar garnets are red and brownish-red to violet. They are called pyrope, almandine and rhodolite. There are also orange garnets and even some that are a vivid green colour. A translucent garnet called tsavorite from East Africa is also gaining in popularity. Translucent, vivid coloured and larger garnets are rare and valuable precious stones. A number of popular gemstones such as grossularite are members of the garnet group. Garnets are formed by nature in an absolutely perfect state and do not need to be processed in any way after they have been mined. It is simply left to the gemstone cutters to reveal the stones’ glittering inner beauty which they achieve through their use of sophisticated cutting equipment.


Opal is a very special type of gemstone. It scatters a dazzling array of blue, green, red and yellow hues when it catches the light. It was the stone of choice of many kings and emperors and it is still very popular today. Opal contains a small amount of water, so it can dry out under extremely dry conditions. In very rare cases, it can even start to crack. Ensuring that it is exposed to a small amount of moisture will be enough to keep it in good condition. Opals are all completely unique; you will never find two the same and they come in a wide variety of forms and colours ranging from white, grey and black. Certain porous opals can be artificially blackened to make them look like the most valuable opal of them all: the black opal. It is very important that you have been told that your opal has been treated in this way because artificially blackened opals are not valuable. Black backing is often glued to a thin slice of opal and a transparent overlay is often glued onto the top. These composite products need to be described as opal doublets or opal triplets. Opals which have been left on or inside their host rock and have been cut together with this rock are becoming ever more popular. These are called matrix opals or boulder opals which is what they are called where they are mined in Australia. They produce an intense display of colour, especially if they have red reflexes which makes them very valuable. They are found in Australia, Hungary, Brazil and Mexico.


The Ancient Egyptians coveted the incomparable green sparkle of the peridot which also used to be called olivine due to its oily appearance. It is not necessary to process peridot in any way. As it is not as hard as many of its fellow gemstones, it is important to be careful if you wear it inside a ring on your finger. Completely transparent specimens of peridot which have been recently discovered in new deposits are finding their way onto the market. Sophisticated cutting techniques breathe life into these beautiful stones. Peridot is mined in places such as Myanmar, Norway, Sri Lanka, Australia, Mexico and the USA. In 1749, a large meteorite was discovered in Yeniseysk in Eastern Siberia. Peridot was discovered in this meteorite which was large enough to cut. It also displayed absolutely flawless crystal formations. Peridot is therefore a gemstone from the cosmos that we still do not know very much about today.


The blood-red ruby is one of the most valuable gemstones. It has been the symbol of passion, ardent love, power and lavish wealth for thousands of years. Only a very few rubies have been found that are naturally both completely clear and have an intense red colour. This explains why it has become customary over the centuries for their colour and clarity to be enhanced through controlled heating processes in their country of origin. Tiny fractures and small indentations can be seen on the surface of less valuable rubies. These imperfections can be filled with a glass-like substance during the heating process. It is important that you have been made aware that your ruby has undergone this process.


The ruby and the blue sapphire are closely related to each other and only vary in their colour. The soothing, deep cornflower blue of a sapphire has captivated people for millennia. Even though blue is the colour most associated with this gemstone, sapphire can also be found in a range of pink hues, from pale pink to a beautiful vivid pink, in golden yellow, orange, purple and green tones, and there are also translucent varieties. Sapphires have been highly valued since ancient times. Flawless, pure sapphires are very rare which is why most of them have been heat treated since time immemorial. The process intensifies the colour and permanently increases the clarity. Heated sapphires are more affordable than perfect sapphires that have been extracted from the ground and left just as nature intended. Recently, sapphires have appeared on the market which have been embedded in a powder that enhances colour and then heated to almost melting point. A thin blue layer of colour then appears on the surface of the stone. These types of diffusion-treated sapphires are much cheaper than natural blue sapphires. It is vital that the buyer has been made aware that the stone has undergone this treatment.


For many cultures, the emerald with its magical power of attraction has symbolised rebirth and abundant life. Its rich green hues summon up the way nature awakens in spring and evoke notions of hope and possibility. An emerald without any inclusions would be a complete rarity because virtually all of them develop their own unique features in the form of tiny fissures which are called Jardin from the French word for garden. Gem specialists are often able to deduce their provenance from these markings. Emeralds must be worn with the utmost care. In recent times, coloured or colourless synthetic resins have been used to treat emeralds instead of the usual oils which harden inside the stone and are virtually impossible to remove. It is important that these types of treatments have been fully declared.


Spinel was only recognised as a mineral in its own right 150 years ago. The rarest and therefore most valuable spinel gemstones are a luminous red colour. There are also numerous colour variations which are primarily pastel tones from pale red through to violet and blue. Spinel is predominantly mined in Myanmar and Sri Lanka where they are found in mines with rubies and sapphires. This explains why many large and famous rubies are in fact spinel. High-quality spinel stones are a rarity which is why they are not often found on the market or in pieces of jewellery even though they are an 8 on the hardness scale and are very durable. It is only possible to cut spinel as it cannot be processed in any way.


The most valuable and rarest topaz stones used to be confused with the much cheaper stone citrine due to the fact that they share the same sought-after colours which range from cognac brown through to salmon-pink. Pink-coloured topaz is quite a rarity and very pale light-blue stones are only seen every now and then. On the other hand, less attractive colourless topaz can be found in large quantities. Synthetically coloured topaz stones are also very common. However, these are in no way more valuable, but are more common because they are more affordable. A reliable jeweller will always provide the customer with unambiguous information about any synthetic colouring that the stones have undergone.


Tourmaline comes in an array of rainbow colours and certainly enriches the entire range of precious and semi-precious stones. Red, yellow, orange, green, blue and violet tourmaline has captivated people for hundreds of years. Green and pink are the dominant colours. The darkest varieties of all colours have usually been heat-treated in order to make them brighter and to increase their vibrancy. Pink tourmaline is also often irradiated to enhance its colour which is a process that cannot be verified.


Tanzanite is a rare and therefore very valuable gemstone. Its blue, purple and violet hues enrich the rich colour palette of the gem stone family exquisitely. It could be said that tanzanite is one of the most beautiful treasures on Earth. As its name suggests, it is mined in East Africa at the foot of Mount Kilimanjaro. Many tanzanite stones are a brownish-green colour when they are in their natural state. It is only when they are subsequently heat-treated that they reveal the typical blue-violet colouration which makes this precious gemstone so highly valued.


Zirconia stones are very vibrant and highly lustrous gemstones which come in a range of intense colours. They have been highly valued since ancient times because of their vibrancy and the fact that they refract light so effectively. Unfortunately, they are not traded very often on the market. They are arguably very hard, scoring a 7 on the hardness scale, however, they are brittle and not particularly suitable for rings. They come in yellow, brown, brownish-red and are less commonly found in pink and green. When they are heated to between 800 and 1000°C, they become translucent or a bluish-green colour.


Although pearls are not stones, they are still one of the most precious substances on Earth. People have loved and treasured the exquisite, iridescent lustre and delicate, silky surface of natural pearls since time immemorial. However, genuine pearls became extremely rare and demand started to far outstrip supply. Pearl culture techniques were developed in Japan around the year 1900. These techniques involve inserting a small piece of membrane from another related shell into a shell, sometimes along with a grain of mother-of-pearl. The small pieces of membrane form in salt water and grow to form cultured pearls thanks to this time-consuming technique. The same technique is also applied to culturing freshwater pearls and South Sea pearls. We differentiate between Akoya cultured pearls, freshwater cultured pearls and South Sea pearls. When pearls are harvested, they do not always fulfil the requirements of the wearer. Virtually all cultured pearls are carefully polished to enhance their lustre. Akoya cultured pearls that have slight imperfections on them are bleached which gives them a delicate pink hue. It is important to ensure that it has been made completely clear to you if the cultured pearls you are considering buying have been made to look a different colour, from any shade from white to grey or yellow, through artificial means or through radiation treatment. Cultured pearls are delicate and should therefore never be stored together with other harder pieces of jewellery. They should also be kept away from cosmetics, perfume, hairspray and solvents. Pearls were highly prized in the Arab world, Persia and India during ancient times. The pearl is generally associated with virginity in Islamic symbolism. Pearls were also highly coveted by the Ancient Greeks and Romans. Pearls used to be called “margarites” which was used as a term to describe a loved one. This term still exists today in the name Margaret. Pearls symbolise wealth, wisdom and virtue in China, in Japan they represent fortune and in India they signify an abundance of children. They also assumed a sacred role during the Middle Ages.

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