Agate is a variety of Chalcedony and forms part of a group of cryptocrystalline quartzes in which the crystals are so tiny that they appear as a solid mass.
Often displaying visible banding patterns, it is a popular choice for jewellery due to its varied appearance and relative hardness, ranging from transparent to opaque.
Varieties include Bloodstone (formerly Heliotrope), Blue Lace Agate, Dendritic Agate, Green Agate, Moss Agate, Fire Agate, Onyx and Sardonyx.
Amethyst is a purple variety of quartz. It’s name comes from the Greek word amethystos, which loosely translates as 'not drunken', as it was believed to offer protection against drunkenness. This is why wine goblets were often carved from it.
Occurring in primary hues from a light pinkish violet to a deep purple, the best varieties of Amethyst can be found in Siberia, Sri Lanka, Brazil and the far East.
Amethyst is the birthstone for February.
Derived from the ancient Greek adámas, meaning ‘unbreakable’, diamond is the hardest known natural material on the Mohs scale. Because it can only be scratched by other diamonds, it maintains its polish extremely well. Unlike many other gems, it is well-suited to daily wear because of its resistance to scratching.
Diamonds are thought to have first been recognised and mined in India for well over 3,000 years. Their popularity has risen since the 19th century due to increased supply, improved cutting and polishing and very successful advertising campaigns.
The methods of grading diamonds based on the characteristics most important to their value as a gem are known as the four Cs. These are: Carat - its weight, Cut - quality of the cut is graded according to proportions, symmetry and polish, Colour - how close to white or colourless (for fancy diamonds how intense its hue is), and Clarity - how free is it from inclusions.
A large, flawless diamond is known as a paragon.
The ancient Romans and Greeks believed that diamonds were the tears of the gods or possibly even splinters that had broken off of falling stars. They were believed to promote strength, invincibility and courage and were often wore as talismans to ward off evil.
Diamond is the birthstone for April.
Emerald is the green variety of the mineral beryl, coloured by trace amounts of chromium and sometimes vanadium.
Its name derives from the Greek word smaragdos meaning 'green stone'. Their colour is the most beautiful, intense and radiant green. It is this lively luminosity which makes the emerald a unique gemstone.
The green of the emerald is the colour of life, of spring and rebirth. For centuries it has also been the colour of beauty and of constant love. In ancient Rome, green was the colour of Venus, the goddess of beauty and love. And today, this colour still occupies a special position in many cultures and religions. Perhaps this is why emeralds have been held in high esteem since ancient times.
Colombia continues to be the world's largest producer of fine emeralds renowned for their vivid green, with a faint tint of blue. The best known deposits being Muzo and Chivor, where emeralds were mined by the Incas in pre-Columbian times. Here you will also find the rare 'trapiche' emeralds which are distinguished by a six-pointed radial pattern made of ray-like spokes of dark carbon impurities.
Zambia is the world's second biggest producer. The emeralds mined here are a fine deep green with good clarity. Other localities include Brazil, Zimbabwe, Madagascar, Pakistan and India.
Very few emeralds are absolutely “clean”, with inclusions often impairing the appearance and evenness of the colour. The numerous crystal inclusions, cracks or fissures which are typical of this gemstone are sometimes described as “jardin” (French for ‘garden’). These imperfections within the stone are unique to each emerald and can be used to identify its origin.
Whilst its good hardness protects the emerald to a large extent from scratches, its brittleness and many internal stresses can make cutting, setting and cleaning rather difficult. Stone cutters developed a special cut just for this gem: the emerald cut. The clear design of this rectangular or square cut with its bevelled corners was specifically designed to maximise the beauty of this valuable gemstone to the full, at the same time protecting it from chipping or breaking.
Today many emeralds are enhanced with colourless oils or resins to fill in surface-reaching cracks, improving their clarity and stability. This is a general trade practice, but it means they react very sensitively to inappropriate treatment. They cannot be cleaned in an ultrasonic bath as this will remove any of the oils in the stone giving them a matt/dull appearance and can significantly change the colour of the stone. Emerald rings should always be taken off before the wearer puts his or her hands in water containing cleaning agents.
Emerald is the birthstone for May.
Garnet is widely known as a deep red gemstone often found in antique jewellery. However it is available in a rich spectrum of colours and varieties.
Notable garnets include: Almandine - red to purplish red, Pyrope - orange red, crimson, or dark red, Rhodolite - purplish red, Spessartite - rich orange to red, Demantoid - light to chrome green and Tsavorite - emerald green.
The word garnet comes from the 14th century Middle English word gernet, meaning 'dark red'. It is derived from the Latin granatus, from granum 'grain, seed'. This is possibly a reference to pomum granatum 'pomegranate', a plant whose fruits contain abundant and vivid red seeds, which are similar in shape, size, and colour to some garnet crystals.
Garnet is the birthstone for January.
Lapis Lazuli is a rock prized for its intense ultramarine blue colour. It consists of several blue minerals (mainly Lazulite) together with varying amounts of Calcite and Pyrite, creating a mottled appearance. Mined in Afghanistan for over 6000 years it has been used as an ornamental material throughout antiquity. Fashioned mainly into cabochons and beads, it has also been used for carvings and hardstone inlays as well as being ground up to create the most valued artists pigment, Ultramarine.
The most desirable material has an even, intense blue colour with a light ‘dusting’ of pyrite crystals.
Opal is an amorphous (shapeless) form of silica, containing up to 20% water trapped in its silica structure. Forming in the crevices of rocks and sometimes fossils. The name Opal was probably derived from the Sanskrit upala, meaning ‘valuable stone’. The Romans thought it was the most precious and powerful of all stones as it displays the colours of every other gemstone.
Almost 95 per cent of all opals come from Australian mines. The remaining five per cent are mined in Mexico, Ethiopia and Brazil.
Opal is known for its unique display of flashing rainbow colours called play-of-colour. There are two broad classes of opal: precious and common. Precious opal displays play-of-colour, common opal does not. This play-of-colour occurs in precious opal because it’s made up of microscopic spheres stacked in a grid-like pattern. As the light waves travel between the spheres, the waves diffract, or bend. As they bend, they break up into the colours of the rainbow, called spectral colours. Giving the opal it’s unique characteristic.
Opal is generally stable, but heat from intense light can cause fracture lines called “crazing”. High heat or sudden temperature changes can also cause opal to fracture. As it isn’t as hard as many other gemstones it is vulnerable to scratches and chips. Care should be taken when wearing opal set jewellery, always remove it before using any cleaning agents as it is attacked by hydrofluoric acid and caustic alkaline solutions.
Opal is one of the birthstones for October.
Pearls are organic gemstones, created when an oyster covers a foreign object with layers of nacre.
Natural pearls are very rare because they are only created by chance.
Today pearls are cultured by Man. Shell beads are placed inside an oyster and the oyster is returned to the water. Later when the pearls are harvested, the oyster has covered the bead with layers of nacre. Most cultured pearls are produced in Japan. In the warmer waters of the South Pacific, larger oysters produce South Sea and black Tahitian cultured pearls, which are larger in size.
Freshwater pearls are cultured in molluscs in rivers, lakes and ponds mostly in China and are less expensive. They are generally more irregular and varied in shape than saltwater pearls.
The quality of pearls is judged by the orient - this is the soft iridescence caused by the refraction of light by the layers of nacre, the lustre, the reflectivity and shine of the surface. Fine pearls do not have any flaws or spots in the nacre: it should have an even, smooth texture. Other factors which affect value are the regularity of the shape, size, and colour.
Pearl is one of the birthstones for June.
Ruby is the pink to blood-red coloured gemstone variety of the mineral corundum. The red colour is caused by the presence of the element chromium. At the same time this element is also responsible for causing a multitude of fissures and cracks inside the crystals when they form, limiting the size to which they can grow. For this reason, rubies of more than 3 carats in size are very rare. It is no wonder that stones with hardly any inclusions are so valuable - with a desirable colour and larger size they can achieve top prices at auctions, and are more expensive than diamonds.
For thousands of years, the ruby has been considered one of the most valuable gemstones on Earth. It has everything a precious stone should have: magnificent colour, excellent hardness and outstanding brilliance. In Sanskrit, rubies are known as ratnaraj, ‘king of the precious stones’.
The Mogok Valley in Upper Burma (now Myanmar) was for centuries the world's main source for rubies. This region has produced some of the finest stones ever mined, often described as “pigeon's blood” red and being the most desired of colours.
Other localities include Sri Lanka, Tanzania, Thailand, Vietnam and most recently Mozambique.
Rubies are traditionally given to celebrate the 40th Wedding Anniversary and are the birthstone for July.
Corundum is the mineral which gives us the second hardest gemstones: ruby and sapphire.
It is the trace elements of iron in corundum which makes sapphire blue, while chromium in rubies makes them red. Sapphire from the Greek sappheiros, meaning 'blue stone’ comes in a range of other colours including, green, yellow, pink and orange. Though it is best known for its myriad shades of blue.
The extremely rare and expensive natural padparadscha is a delicate light to medium toned pink-orange to orange-pink hued corundum. Originally found in Sri Lanka, there are also deposits in Vietnam and parts of East Africa. The name is derived from the Sanskrit ‘padma ranga’, padma meaning lotus and ranga colour, a shade akin to the lotus flower.
From Antiquity, gemstones have been thought to possess mysterious powers. Sapphire is said to enhance creativity and to focus purity of thought. It is known as the stone of new love and commitment and is claimed to be useful in encouraging faithfulness and loyalty. Making it a popular choice for engagement rings - the most famous being the 12 carat Ceylon sapphire ring, originally belonging to the late Diana, Princess of Wales, and now the Duchess of Cambridge.
Sapphire is the birthstone for September.
Spinel was often confused for ruby throughout history: the most famous being the Black Prince's ‘ruby’ set in the Imperial State Crown of England, which is in fact a magnificent 170-carat red spinel. The reason for the confusion was simple: both stones can be similar in colour and occur in the same localities.
Spinels come in a range of colours from rich reds, to shades of pink, purple and black. They can also be found in beautiful blue - green tones, but these are rarer.
The rarity of large stones is probably the reason why spinel is not better known.
Topaz is a fluorine aluminium silicate - the most common natural colours it is found in are yellow, yellow-brown, pale pink, light to medium red, blue and colourless.
The most expensive and desirable colours are sherry topaz (reddish orange), imperial topaz - a fine apricot orange and pink topaz.
The 1,680 carat Braganza diamond, which was set in the Portuguese crown, was thought to be the biggest diamond ever found. It is now considered to be a colourless topaz which was discovered in Minas Gerais in Brazil in the 18th century.
Topaz is the birthstone for November.
Tourmaline is a much favoured stone amongst jewellery designers and gem enthusiasts alike as it can be found in a great range of colours, more than any other known gemstone. It’s name derives from the Sinhalese (Sri Lankan) words tura mali meaning mixed colours.
Gemstone varieties include rubellite, indicolite, paraiba, dravite, watermelon tourmaline, and schorl.
When heated or rubbed, tourmaline acquires an electric charge and attracts small objects like dust, ashes and other lightweight objects. This phenomenon is known as pyroelectricy, and is considered to be a unique property.
Tourmaline is believed to inspire creativity and was used extensively as a talisman by artists and writers during the renaissance through the late 1800s. It is one of the birthstones for October.