Beryl – a guide to this enigmatic gemstone family
(Beryl can be found in a range of colours and hues)
The beryl family comprises stones of beryllium aluminium cyclosilicate, the best known examples of which are aquamarine and emerald. However there are also many other sub-classes to this multi-coloured family that are starting to grow in popularity. Pure beryl is actually colourless but it is almost nonexistent in nature and the stones of this group are best known for the coloured varieties, which can be grouped into green, blue, yellow, red and white. Red beryl is actually the rarest of the family but emerald is by far the most valuable. The etymology of the name can be traced to the Latin beryllus, later adapted into many different languages and subsequently anglicised to beryl. Interestingly many, often surprising, uses have been found for beryl over the years including its use by pioneering 13th century Venetian telescope makers, who discovered that it was clearer than the glass available at the time. In terms of the geology in which beryl is found, it is most common in granitic pegmatites but it also occurs in mica schists in the Urals and limestone in Colombia. Beryl has been mined in a wide variety of locations, including Norway, Austria, Germany, Sweden, Ireland, Russia, Brazil, Colombia, Madagascar, Mozambique, Pakistan, South Africa, USA, Zambia, Afghanistan and more recently in Ethiopia. Some of the largest beryl have been unearthed in Madagascar, with one example measuring 18 by 3.5 metres and a weight of 380 tonnes!
Aquamarine is a blue or cyan variety of the beryl family and it is mostly found in areas containing ordinary beryl. The etymology of aquamarine hails from the Latin acqua marina, translating as ‘of the sea.’ Large deposits are located in Sri Lanka and a clear yellow variety, often referred to as aquamarine chrysolite, is found in Brazil. A deep ocean blue coloured aquamarine known as maxixe has been produced in Madagascar but its colour tends to fade to white when exposed to sunlight or heat treatment (a process that can be reversed by irradiation). Aquamarine has also been discovered at the summit of Mount Antero, Colorado, in the Big Horn Mountains, Wyoming and the Sawtooth Range, Idaho, USA. The Brazilian aquamarine mines are to be found in the states of Minas Gerais, Espírito Santo, Bahia, and Rio Grande do Norte. Colombia, perhaps better known for its emerald production, also supplies aquamarine, as do Zambia, Madagascar, Tanzania and Kenya. The biggest gem quality aquamarine every won was discovered in Minas Gerais, Brazil, in 1910 and weighed over 110 KG and measured almost half a metre in length and diameter. The largest cut example is the Dom Pedro aquamarine, now in the possession of the Smithsonian Institute.
Emerald is a green beryl coloured by trace elements of chromium and vanadium and most are moderately to heavily included with numerous fissures, making them quite brittle. The origin of the name stems from the Latin Esmaraldus, meaning green gem. Throughout early history emeralds were produced in Austria, the Swat valley (in modern day Pakistan) and notably Egypt, where Cleopatra adorned herself with these gems. The ancient Aztecs and Inca civilisations discovered emeralds in modern day Colombia thousands of years ago and these were quickly exploited by the Spanish Conquistadores when they arrived from Europe from the 1490s onwards. A very rare type of Colombian emerald, known as a ‘trapiche,’ exhibits a ‘star’ pattern (and is sometimes referred to as a ‘star’ emerald) comprising a 6 pointed radial pattern, named after the trapiche grinding wheel used to process sugarcane in the region. Colombian emeralds are the most sought after in the world due to their transparency, colour and fire and are most commonly found in the regions of Muzo, Coscuez and Chivor. Fine emeralds are also produced in Zambia, Brazil, Zimbabwe, Madagascar, Pakistan, India, Russia, USA and Ethiopia. Due to the value of gem quality emeralds many attempts have been made to produce synthetic versions, utilising both hydrothermal and flux-growth techniques.
Golden beryl can be found in a spectrum from pale yellow to a brilliant yellow-gold and the stones contain very few inclusions. The name is derived from the Greek hēlios, meaning “sun” and is not to be mistaken for heliodor, a more greenish-yellow shade of beryl. In both stones the yellowish colouration is caused by the presence of ferric iron impurities. One of the finest examples of yellow beryl is the flawless 2,054 carat stone on display in the Hall of Gems, Washington D.C.
This is the colourless form of beryl, owing its name to its discovery in Goshen, Massachusetts. Several elements act as inhibitors to colour in beryl so it is not true to say that goshenite is the ‘purest’ beryl and its gem value is relatively low. Goshenite is to be found in almost every beryl producing locality and it has been used extensively in the past for the manufacture of lenses and optics, due to its transparency. However its modern day uses are largely limited to jewellery and as a source of beryllium. It is possible to colour goshenite yellow, green, pink, blue and intermediate colours with high-energy particles.
Morganite is sometimes referred to as “pink emerald,” “pink beryl,” “rose beryl” and “cesian (or caesian) beryl.” As these names imply, it is predominantly light pink member of the beryl family, although it can also be found in orange and yellow. Unlike emerald, it can be heat treated and/or irradiated to improve its colour. First discovered in Madagascar in 1910, and originally referred to as pink beryl, it was named ‘morganite’ by the New York Academy of Sciences in honour of its primary benefactor, the financier J.P. Morgan. The largest example was discovered in 1989 at the Bennett Quarry in Buckfield, Maine, USA. It was named the “Rose of Maine” and measured 23 cm by 30 cm and weighed 23 KG.
Red beryl was formerly referred to as “bixbite” and it was commonly advertised as “red emerald” or “scarlet emerald.” It was discovered in Utah, USA, in 1958 by Lamar Hodges and it is extremely rare, having only been discovered in a handful of locations in the US, including: Wah Wah Mountains, Beaver County, Utah (the largest source of production); Paramount Canyon and Round Mountain, Sierra County, New Mexico and Juab County, Utah. Red beryl is also produced synthetically and akin to emerald (but unlike most other beryl varieties) it is often heavily included. Whereas most gem beryl is to be found in pegmatites and some metamorphic rocks, red beryl occurs in topaz-bearing rhyolites. It is formed by a crystallisation process that occurs under low pressure, high temperature conditions from a pneumatolytic phase along fractures or within miarolitic cavities of the rhyolite, usually found near the surface.
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