Beryl is commonly associated with its two most famous forms, emerald and aquamarine but there is more to this mineral than that

As a matter of fact, most beryl is not even gemstone quality and as such, its prime importance lies in its being the main industrial source for the element beryllium, which finds application in the nuclear and aerospace industries. Common beryl has been mined for beryllium since as long ago as 1925.

Before we move on to a description of the gem varieties of beryl, let us take a look at beryllium, recently infamous in gem circles for its presence in heat-treated orange sapphires. Beryllium is a chemical element in the periodic table and its atomic number is 4. In its pure form, it is a steel grey, strong, light-weight yet brittle alkaline earth metal and is used as a hardening agent in alloys, most notably beryllium copper, which due to its electric and thermal conductivity, high strength and hardness, non-magnetic properties, and high corrosion and fatigue resistance finds application in defence and aerospace for high speed aircraft, missiles, space vehicles, communication satellites, etc. However, it must be noted that

beryllium and its salts are all toxic and carcinogenic (cancer causing). The good news though, is that when it occurs as the mineral beryl, it is harmless and can safely be worn everyday.

Beryl itself is a silicate mineral with a very unusual composition. It forms as a ring silicate that is the silicate tetrahedra are linked to form rings. In its pure form, it is colourless and differing trace elements in the crystal lattice allow for its range of bright colours without which, it would be an insipid and uninspiring gem due to its relatively low refractive index and low dispersion that account for its diminished brilliance.

Gem beryl is almost exclusively found in hydrothermal veins, pegmatites or at the contacts of larger igneous instrusions that invade aluminous schist, shale or impure limestone. Before we move on to emeralds and aquamarines, which is what most people think of  when

beryl is mentioned, let us takea look at the lesser known forms of this gem group.

Goshenite is the name applied to a variety of clear beryls. It is named after a deposit where it was found in Goshen, Massachusetts. Since we have already mentioned earlier that beryl in its pure form is devoid of colour, it is understandable if the assumption is made that goshenite therefore is the purest form of this mineral. However, a little known fact is that there are several elements that can act as colour inhibitors in beryl and so the absence of hue may be due to some impurity rather than a lack of it.

Goshenite is found in all locations where any form of beryl is found. Its main application in the gem industry has been to use it with metal foil to imitate the colours of emerald and aquamarine. Due to its limited fire and lack of any attractive hue, it is not a popular gem even though it is inexpensive. It is said that the ancient Greeks used colourless beryl as lenses so it is possible that the first spectacles on earth were made of beryl.

The most popular of the other beryls is morganite, which comes in the colour range of pastel pink to peach to lavender. The colour is due to trace amounts of manganesethat finds its way into the crystal structure of the stone. Morganite derives its name from that of the famous American industrialist J.P. Morgan. It was first discovered in California's Pala pegmatites in 1905 and later in Madagascar. There are also deposits found in Afghanistan, Brazil, Mozambique,

Namibia and Russia. Most of the material found comes from mainly three sources: the Pala and Mesa Grande districts in San Diego, California, the Urucum and Benanal mines in Minas Gerais, Brazil and the Mt. Bity region in Madagascar. All are pegmatite occurrences.

Being a relatively rare stone, it does not occur in large enough quantities like its famous cousins to build and international market or create consumer demand for it. Therefore it is limited to being a collector's stone. Also, stones of rich apricot and peach colours have been known to fade to a pale pink and that too is a minus point where desirability is concerned. The largest faceted morganite is a approximately 600-carat cushion shaped stone from Madagascar that is now in the collection of the British Museum.

Heliodor or golden beryl is named after the Greek words for sun (helios) and gift (doron). However if the stone lacks the golden tint, it is not called heliodor but rather only yellow beryl. Heliodor was first discovered in Namibia in 1910, in a pegmatite that also produced aquamarine. Like Aquamarine, heliodor also owes its colour to the presence of iron impurities in the beryl structure. The colour ranges from pale yellow to yellow-orange and yellow-green depending on both, the concentrations of Fe²⁺ and Fe³⁺ as well as on where these impurities are located in the beryl crystal structure.

Beryl's crystal structure contains channels outlined by rings of (Si-O)6 units. These rings are stacked upon one another leaving space within the channels for water or other impurities. Colour influencing iron impurities can be present in these interstitial channel sites or substituting for aluminium in octahedral sites. When Fe³⁺ is present substituting for aluminium in an octahedral site, the yellow colour of heliodor is created. When Fe²⁺ is present in the interstitial channel site, a pure blue colour results. When they are both present, than we get the typical blue-green hues of aquamarine. Heating heliodor to 200-250 degrees Celsius can expel the Fe³⁺ and Fe²⁺ thus eliminating the yellow colour and producing either colourless or blue beryl. Irradiation can reverse this process and restore the yellow colour though.

Heliodor occurs mainly in granite pegmatities and to a lesser extent in miarolitic cavities in granites and in greisens. It is typically associated with quartz, feldspars and muscovite and often occurs with other pegmatite accessory minerals like garnet, spodumene, topaz, tourmaline, tin and tungsten minerals, etc. Because of its relatively high hardness and  specific    gravity,   it  is    sometimes    found    in 

Emerald owes its green to traces of vanadium and chrome. The fascinating thing about this is that these elements occur concentrated in the earth's crust at completely different locations from beryllium and therefore logically, emeralds should not exist at all. However nature delights in exceptions and emeralds are the happy result of extreme tectonic processes that bring these two elements together and crystallise them under conditions of high temperatures and enormous pressure. Due to the manner of its genesis, emerald rarely occurs in clean crystals especially in the larger sizes. The flaws and inclusions are so much a part of this   stone   that   a   vivid   green   coloured    gem   with

inclusions is preferred to one with a pale colour and  noflaws. The crystal inclusions or fissures that are typical of emeralds are refered to by experts as "jardin", which is French for garden. The name emerald itself derives from the French "esmeraude", which in turn goes back via Latin to the ancient Greek root "smaragdos" which simply means green gemstone.

Colombia is the main country of occurrence for fine emeralds. About 150 mining sites are known there, however not all are currently being exploited. The most famous names in this context are Muzo and Chivor, where even in pre-Colombian times the Incas mined emeralds. The economically most important mine is Coscuez. Estimates ascribe about three quarters of the current Colombian emerald production to the about 60 locations belonging to the Coscuez mine. Colombian emeralds are set apart from those of other origin by their especially fine and brilliant green, which is not influenced by any bluish tinge.

One of the largest emeralds in the world is the "Moghul Emerald", whose history has been traced back to 1695. It is 10 cm. high, weights 217.80 carats and is inscribed with prayers on one side and engraved with flowers on the other. Christies London sold it to an anonymous buyer for $2.2 million at an auction. Other famous emeralds are mostly in museums or state treasuries. The New York Museum of Natural History has a pure emerald cup said to have been owned by the Moghul Emperor Jehangir as well as a Colombian emerald crystal weighing 632 carats. The Bank of Bogota has in its collection at least five emeralds weighing between 220 to 1796 carats. Their size might be rivalled by the splendour of some truly amazing specimens in the Iranian state treasury among which is the tiara of the last Iranian Empress Farah.

This brings us to the last of the main gems in the beryl group, aquamarine, which literally means sea-water. It's blue-green colour and shimmery radiance certainly live up to the name. Legend says that it is the treasure of mermeids and a powerful charm for salilors with more power when immersed in water. In centuries past, most sailors did not know how to swim and the sea faring profession was an extremely hazardous one, so a powerful charm was very welcome.

Aquamarines are usually pastel blue in colour. The darker the colour, the better it is judged to be and a more  prominent  blue

found in Afghanistan, Ireland, Russia, the Indian sub-continent and the USA. An unusual type of aquamarine found in Minas Gerais displays asterism. Some similar material is also found in Madagscar. Cat's eye aquamarine is seldom seen on the market.

So this then is the beryl group of minerals, interesting and full of surprises and of course immensely beautiful. From the rare to the easily available, they can only add to the value of a collector's store and a deeper knowledge of these stones can only serve to increase our appreciation of them.