Zircons have great brilliance and intense dispersion but are brittle, making them sensitive to knocks.

The major deposits of zircons occur in Burma, Australia, Brazil, Madagascar and Sri Lanka.

Turquoise has been used for thousands of years by ancient civilizations such as the Persians, Egyptians, Aztecs and Tibetans. The stone in its purest form has a waxy or sleepy appearance with a sky blue colour and is often mixed with a black or brown matrix.

The best turquoise comes from north Iran and is still available but has been overwhelmed by cheap treated low quality material.

It is usually assumed that most turquoise is treated nowadays unless stated otherwise. Common treatments include resin impregnation, blue dyes, oiling, mixtures of glass and plastics etc.

Most blue topaz sold in the jewellery trade today is treated to give the stone its permanent blue colour. The colours range from soft pale sky blue to a medium Swiss blue through to an electric steel London blue.

Some care must be taken when setting topaz as it subject to cleavage if knocked or put under excessive pressure.

(See also Topaz Birthstone)

In larger stones tanzanite has a unique and intense blue purple colour that is a cross between amethyst and a blue sapphire. Despite its short history Tanzanite has become a highly desired and popular stone in the jewellery trade.

Tanzanite is a soft stone and slightly brittle and requires extra care when being set and cleaned.

Sapphires are found in a range of blues from deep dark royal blues of Australia to a soft pastel and corn flower blues of Sri Lanka (Ceylon type). Superb yellows from pale soft buttery colour to vivid golden yellows which are highly sought after are becoming more expensive if untreated and natural in origin.

Green sapphires from Australia or Sri Lanka usually show classic bottle or olive green colours with some secondary yellow hues. One of the most highly sought after colours are pink sapphires these range from hot pinks to subtle blends of pinkish purple and are sourced from Sri Lanka and Madagascar.

Sapphires, know as parti stones, are also highly sought after as they show two distinct colours in the same stone such as blue and yellow, and can command high prices.

Sapphires are found throughout the world with major deposits in Australia, Sri Lanka, Burma, Thailand and increasingly Africa.

Tourmaline is a gemstone that is found in various colours  including pale to intense pinks, light blue, steel blue, green-blue, various shades of green and yellow-brown to dark brown.

Tourmaline also comes in multi-colours the most well known being the watermelon that is a combination of pink and green. Blue and green crystals tend to be long and thin and therefore are often cut as baguette or emerald cuts, pinks are often also found as ovals and fancy cuts.

Tourmalines make beautiful pendants and earrings, they are also often used in dress rings however must be treated with care.

Brazil is the major source of tourmaline however it is also found in deposits in many locations around the world.

Since the 19th century Australia has become the major source of precious opal.  Precious opal ranges in colour from opaque whites with little flashes of colour to the most desired black opal that has a dark background with large patches of intense colours including reds, greens and blues.

Other varieties of Australian opal include crystal opal, a transparent gem with strong play of colour and boulder opal consisting of a natural ironstone backing with a thin top layer of colourful opal.

Opal may be purchased as a solid cabochon or as the less valuable doublet or triplet.  A doublet consists of a thin layer of fine natural opal bonded to a dark backing. A triplet also consists of a thin layer of fine opal bonded to a dark backing and a transparent quartz top. These stones require careful handling and care so as not to damage them.

Most precious opals are cut as cabochons and show play of colour as the gems are observed from different angles.

Most opals are individual pieces that lend themselves to interesting designs for rings and pendants.

Peridot was introduced into Europe in the Middle Ages by the crusaders and was often used in ecclesiastical jewellery and adornment.

Main deposits include the original historical mines of Zebirget Egypt, Pakistan, Sri Lanka, Burma and China.

Ruby colours do vary depending on the origin of the stone and stones often show secondary hues of colour including browns, purples, pinks and even blues. These stones are usually heat treated to minimize the secondary hues of colour and enhance the redness in the stone. Rarer but just as beautiful and desirable are star rubies which show a 6 rayed star when the stone is cut into a cabochon shape.

Some of the most important deposits of ruby include Burma, Thailand, Sri Lanka and in more recent times Madagascar and Tanzania.

Pearls can be classified into various types, the natural pearl which grows without any human intervention is very rare and only accounts for a tiny fraction of the modern pearl market. Cultured pearls are the result of a small bead being implanted into the soft tissues of the oyster to produce an irritation which ultimately becomes the pearl. These types of cultured pearls included the Japanese Akoya pearls which are found in the coastal water of Japan.

The South Sea cultured pearls consist of white, black and golden coloured pearls which are found in tropical waters of Australia, Indonesia, Tahiti, and The Philippines. These pearls are prized for their large size and lustre and are the standout in the pearl world. The freshwater cultured pearl in produced in large quantities in freshwater dams in China and has continued to supply an affordable pearls in ever increasing sizes and quality.