BERYL

BERYL - We have already discussed some of the beryllium gems, namely emerald and aquamarine, but we should also mention the lesser-known members of the same family. Green Beryl, without the chromium that makes it emerald, is common and, because of its colour, is not particularly attractive. However, it is used in doublets and triplets to simulate emerald. Heliodor or yellow beryls, with shades varying from pale to rich gold, are found in the same locations as aquamarine. As with the latter it is often free of inclusions. Morganite is a pink variety named after the American banker and philanthropist Henry Pierpoint Morgan. It comes in shades of rose and peach as well as pink. Morganite is mainly translucent; cat’s-eye varieties have been found. It is generally pale, though dark shades from Madagascar (formerly the Malagasy Republic) and Afghanistan may show dichroism. Its other main source is the USA. Synthetic transparent pink beryls are now grown in Russia. Red Beryl or Bixbite in good gem quality is very rare and, as such, remains a collector’s item. It is sometimes misleadingly referred to as ‘red emerald’. A deeper blue of beryl darker than aquamarine has been recently discovered in Canada. A colourless variety (Goshenite) is also found.

BENITOITE

BENITOITE - Discovered in America in 1907, this gem was originally thought to be sapphire due to its beautiful blue colour, but was later found to be an entirely new variety.It has a hardness of 61/2 on the Mohs scale, shows excellent fire, and is strongly dichroic (blue and colourless). Its dichroism differentiates it from sapphire, as the latter does not have a colourless ray. Benitoite is rare as it is only found in one part of the USA. It is a very valuable and expensive gem and needs care in its handling. It is the official state stone of California. Benitoite also occurs in a pink variety.

ANDALUSITE

ANDALUSITE
An attractive gemstone, the andalusite takes its name from Andalusia in Spain, where it was first discovered. It has since also been found in Sri Lanka and Brazil.

Andalusite has a hardness of 71/2 on the Mohs scale, so is very suitable for a ringstone. It is extremely pleochroic: it shows different colours in different directions – yellow, green and red. If you are after something distinctive, this stone will fit the bill.
Similar shades of tourmaline are sometimes passed off as andalusite, but they lack the pleochroism
Chiastolite, an impure opaque variety of andalusite, is found in the Pyrenees. The carboniferous inclusions form a cross, hence its other name: ‘Cross Stone’. It
also occurs in several other locations around the world. Andalusite has two associa¬ted gems, termed polymorphs: Sillimanite and Kyanite, which are occasionally cut and used in jewellery. Although hard, they are somewhat fragile, so the choice of mount is important.
Sillimanite occurs in many countries. Rarely transparent, suitable stones for mounting are an attractive pale or violet blue.
Kyanite occurs in blade-like crystals in colours approaching the blue of sapphire. The size of cut gems is limited due to the crystal form, which has the very unusual property of having two hardnesses, 7 in one direction and 4 in the other, causing problems when faceting.

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