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Alexandrite

This rare gemstone is named after the Russian tsar Alexander II (1818-1881), the very first crystals having been discovered in April 1834 in the emerald mines near the Tokovaya River in the Urals. The discovery was made on the day the future tsar came of age. Although alexandrite is a relatively young gemstone, it certainly has a noble history. Since it shows both red and green, the principal colours of old Imperial Russia, it inevitably became the national stone of tsarist Russia.

Beautiful alexandrite in top quality, however, is very rare indeed and hardly ever used in modern jewellery. In antique Russian jewellery you may come across it with a little luck, since Russian master jewellers loved this stone. Tiffany’s master gemologist George Frederick Kunz (1856-1932) was also fascinated by alexandrite, and the jeweller’s firm produced some beautiful series of rings and platinum ensembles at the end of the 19th and beginning of the 20th century. Smaller alexandrites were occasionally also used in Victorian jewellery from England.

The magic of changing colours

The most sensational feature about this stone, however, is its surprising ability to change its colour. Green or bluish-green in daylight, alexandrite turns a soft shade of red, purplish-red or raspberry red in incandescent light. This unique optical characteristic makes it one of the most valuable gemstones of all, especially in fine qualities.

Alexandrite is very scarce: this is due to its chemical composition. It is basically a chrysoberyl, a mineral consisting of colourless or yellow transparent chrysoberyl, chrysoberyl cat’s eye and colour-changing alexandrite (also in cat’s eye varieties). It differs from other chrysoberyls in that it not only contains iron and titanium, but also chromium as a major impurity. And it is this very element which accounts for the spectacular colour change. Rarely, vanadium may also play a part. According to CIBJO nomenclature, only chrysoberyls displaying a distinct change of colour may be termed alexandrite.

Like many other gemstones, alexandrite emerged millions of years ago in a metamorphic environment. But unlike many others, its formation required specific geological conditions. The chemical elements beryllium (a major constituent in chrysoberyl) and chromium (the colouring agent in alexandrite) have contrasting chemical characteristics and do not as a rule occur together, usually being found in contrasting rock types. Not only has Nature brought these contrasting rock types into contact with each other, but a lack of the chemical element silica (the second most common element in the Earth’s crust) is also required to prevent the growth of emerald. This geological scenario has occurred only rarely in the Earth’s history and, as a result, alexandrite crystals are very scarce indeed.

Nowadays not only from Russia

Russia has remained the primary source of alexandrite since gems from the mines of the Urals became available on the market. When the Russian deposits were thought to have been exhausted, interest in the unique colour miracle decreased - especially since alexandrites from other mines hardly ever displayed the coveted colour change. But the situation changed dramatically in 1987, when alexandrites were discovered in a place called Hematita in Minas Gerais, Brazil. The Brazilian alexandrites showed both a distinctive colour change and good clarity and colour. Thus the somewhat dulled image of the miraculous stone received another boost. The colour of the Brazilian stones is admittedly not as strong a green as that of Russian alexandrite, but the colour change is clearly discernible. Today Hematita is one of the most important deposits of alexandrite in economic terms. Occasionally alexandrite with chatoyancy is discovered there, an effect which has not yet been observed in Russian alexandrite. Alexandrites are also obtained from sources in Sri Lanka, but the hue of these stones compares less than favourably with that of the Uralian alexandrites. They appear green in daylight and a brownish red in artificial light. The Tunduru area in southern Tanzania has also produced some outstanding specimens since the mid-1990s. Alexandrites are also found in India, Burma, Madagascar and Zimbabwe. Although this stone is still considered a rarity, specialised gemstone dealers do stock it, especially since improved trade relationships between Russia and the rest of the world have ensured a better supply of Russian alexandrites to the market.

A gemstone for experts and gemstone lovers

With its good hardness of 8.5, alexandrite is an uncomplicated stone to wear. The more distinct the change of colour, the more valuable the stone. A fine alexandrite should show a vivid bluish-green in daylight and a purplish-red in artificial light, without any trace of undesirable brown or grey. If the origin of the stone is known beyond dispute to be Russia, we are talking about a real rarity of enormous value. Finely faceted alexandrites above one carat are thus among the most expensive gemstones in the world, rarer than fine ruby, sapphire or emerald.

Alexandrite is a stone for experts, enthusiasts and connoisseurs, a true understatement stone. Its uniqueness and high value are not evident at first sight. The mysterious colour change will only occur on exposure to different light sources. But if you really get involved in alexandrite, you will be utterly fascinated by this gem. Maybe you will also feel some of the mysterious magic and lore ascribed to it. It is considered a stone of very good omen. In critical situations it is supposed to strengthen the wearer’s intuition, and thus help him or her find new ways forward in situations where logic will not provide an answer. Alexandrite is also reputed to aid creativity and inspire the imagination.

This months birthstone is Emerald, it is the gemstone most associated with Ireland. Emeralds are fascinating gemstones. They have the most beautiful, most intense and most radiant green that can possibly be imagined: emerald green. Inclusions are tolerated. In top quality, fine emeralds are even more valuable than diamonds.

The name emerald comes from the Greek ’smaragdos’ via the Old French ‘esmeralde’, and really just means ‘green gemstone’. Innumerable fantastic stories have grown up around this magnificent gem. The Incas and Aztecs of South America, where the best emeralds are still found today, regarded the emerald as a holy gemstone. However, probably the oldest known finds were once made near the Red Sea in Egypt. Having said that, these gemstone mines, already exploited by Egyptian pharaohs between 3000 and 1500 B.C. and later referred to as ‘Cleopatra’s Mines’, had already been exhausted by the time they were rediscovered in the early 19th century.

Written many centuries ago, the Vedas, the holy scriptures of the Indians, say of the precious green gems and their healing properties: ‘Emeralds promise good luck …’; and ‘The emerald enhances the well-being …’. So it was no wonder that the treasure chests of Indian maharajas and maharanis contained wonderful emeralds. One of the world’s largest is the so-called ‘Mogul Emerald’. It dates from 1695, weighs 217.80 carats, and is some 10cm tall. One side of it is inscribed with prayer texts, and engraved on the other there are magnificent floral ornaments. This legendary emerald was auctioned by Christie’s of London to an unidentified buyer for 2.2m US Dollars on September 28th 2001.

Emeralds have been held in high esteem since ancient times. For that reason, some of the most famous emeralds are to be seen in museums and collections. The New York Museum of Natural History, for example, has an exhibit in which a cup made of pure emerald which belonged to the Emperor Jehangir is shown next to the ‘Patricia’, one of the largest Colombian emerald crystals, which weighs 632 carats. The collection of the Bank of Bogota includes five valuable emerald crystals with weights of between 220 and 1796 carats, and splendid emeralds also form part of the Iranian National Treasury, adorning, for example, the diadem of the former Empress Farah. The Turkish sultans also loved emeralds. In Istanbul’s Topkapi Palace there are exhibits with items of jewellery, writing-implements and daggers, each lavishly adorned with emeralds and other gems.

Diamond is the ultimate gemstone, having few weaknesses and many strengths. It is well known that Diamond is the hardest substance found in nature, but few people realize that Diamond is four times harder than the next hardest natural mineral, corundum (sapphire and ruby). But even as hard as it is, it is not impervious. Diamond has four directions of cleavage, meaning that if it receives a sharp blow in one of these directions it will cleave, or split. A skilled diamond setter and/or jeweler will prevent any of these directions from being in a position to be struck while mounted in a jewelry piece.
As a gemstone, Diamond’s single flaw (perfect cleavage) is far outdistanced by the sum of its positive qualities. It has a broad color range, high refraction, high dispersion or fire, very low reactivity to chemicals, rarity, and of course, extreme hardness and durability. Diamond is the April Birthstone.
In terms of it’s physical properties, diamond is the ultimate mineral in several ways: 
• Hardness: Diamond is a perfect “10″, simply the hardest substance known by a wide margin.
• Clarity: Pure diamond is completely colorless and transparent over a larger range of wavelengths (from the ultraviolet into the far infrared) than is any other solid or liquid substance - nothing else even comes close.
• Thermal Conductivity: Diamond conducts heat better than anything - five times better than the second best element, Silver! This characteristic is the basis for “diamond tests”, as it is simple and cannot be faked.
• Dispersion: Diamond has a relatively high optical dispersion which gives diamond the “fire” that makes it so desirable.
Diamonds may be nearly any color in the rainbow plus browns, grays, and white. Shades of yellow are most common, followed by colorless. Blue, black, reddish, and greenish are more valuable (some extremely so).
Diamonds are found in a type of rock called “Kimberlite”, which comprises the core of certain volcanoes over especially thick portions of the earth’s crust.  This hard stone is mined and then crushed between giant steel rollers.  The kimberlite is reduced to fine gravel, yet the extremely hard diamonds come out unharmed!  Water is added and a grease covered roller sorts the diamonds from the gravel, as the diamonds stick to the grease. Typically, a single carat of diamond is recovered from a ton of ore.
Diamonds are found in many areas including South Africa, Russia, and even in Arkansas in the USA.  In all cases, diamonds formed deep within the earth’s mantle, and were brought to the surface in volcanic eruptions.  In many cases, the diamonds weathered out of the kimberlite by natural processes, and were transported downstream by water.  Many diamonds are mined in the resulting alluvial deposits in areas such as along the coast of South Africa.

The gemstone aquamarine is the blue, or perhaps more correctly, blue-green or aqua variety of the mineral beryl and it is the birthstone for March.
Other gemstone color varieties that belong to beryl include emerald, morganite, and heliodor.
Aquamarine is colored by trace amounts of iron that find their way into the crystal structure. Most gem aquamarines have been heat treated to produce the popular blue-green colors from less desirable yellow or pale stones. The leading producer of aquamarines is the country of Brazil, which has many mines. Pakistan, as well as many U.S. localities, produce wonderful specimens as well. Recently, a new mine in China has produced large numbers of excellent flat (stubby) hexagonal crystals, for a fraction of the price of those beautiful Pakistan specimens.
Aquamarine is sometimes found in huge crystals (unlike emerald).  It is also known in a glassy form, often without showing crystal form, and sometimes with many holes or other odd shapes.  Other times a large cluster of prismatic crystals can be seen to all have the same alignment - a sign that it is really a single crystal with many faces.