October Birthstone: Opal

Opals come in a variety of colours

Opals are most prized for their unique fiery play of colour, reflecting and refracting light into brilliant flashes of multiple colours. The true source of this play of colour was mistakenly attributed to Adularescence until the invention of the scanning electron microscope. Subsequent  analysis at 20 000 time magnification uncovered the true cause of the effect we know today as Opalescence.

Opal is hydrated silicon dioxide, containing from three to twenty percent water. This feature coupled with its low hardness of 5.5 - 6.5 on the Moh's scale, means that Opals require special care as a gemstone

Colours: Various
Hardness: 5.5 - 6.5
Refractive Index: 1.37 - 1.52
Specific Gravity: 1.98 - 2.50
Crystal System: Amorphous
Enhancements: May be enhanced
Major Sources: Mexico, Australia, Tanzania, Zimbabwe, Brazil

Warnings for Care
Soft, brittle  very susceptible to physical damage / heat

Opal Facts
Opal has a distinguished history dating back to pre Greek, Indian Sanskrit times. The name is derived from  the Indian Sanskrit word for stones  "upala". Three groups of Opal exist, precious opal, fire opals and common opals.

Opal - What Causes the Colour
The body colour or matrix in Opal  can be white, colourless, pale yellow, pale red, brown, gray or black depending on the host rock and the level of impurities.  Internal diffraction of light causes  flashes of any color across the entire spectrum (opalescence). The physical structure of opal is unique, with tiny spheres of silicon dioxide having orientated themselves during the solidification of a mineraloid gel, into pyramid shaped grids interspersed with water molecules.  A combination of the size and spacing of the spheres and tiny natural faults between the grid layout, causes light to be split into its constituent spectrum of colours, which results in the characteristic play of color. While the diffraction and interference can express itself as every colour in the visible spectrum, each Opal is unique in terms of its internal structure and the colours observed. Precious above all other varieties displays multispectral hues that change with the angle of observation.

Precious Opals
Black Opal, is the "King of Opals" which is a precious opal with black matrix color. The high contrast between the matrix and the opalescence ensure this variety has the highest play of colour.  White Opal, is also considered a precious Opal with white or very light matrix colour.

Fire Opals
Fire Opals are names after their orange colour, they do not opalesce and are generally milky or turbid in appearance.

Common Opals
Common Opals are mostly opaque, and devoid of the characteristic play of colour seen in Precious Opals.

Purchasing Opal
When choosing an opal, the lay of colour, matrix color and degree of transparency are the most important criteria which determine the price of precious opals.

While popular Opals are delicate gemstones, prone to dehydration, cracking, scratching and fading. When not being worn it is suggested that they be kept in a humidified environment (60-70%) such as in a plastic bag with a pierce of damp cotton wool, or in a cigar humidor.  For jewellery pieces Opals are better suited for earrings, brooches, and pendants, than rings and bracelets.

Colour
The higher the play of colour and the darker the matrix (for contrast) the more expensive the stones. The exception is Harlequin Opals, where the play of light can be relatively simple but the pattern in important with strong geometrical pattern being sold at a premium

Lighting
Opal looks best viewed in natural especially in the softer early morning or late evening light where the play of colour is maximised.

Clarity
Precious Opal are acceptable in, opaque, transparent or  translucent grades of clarity. The latter are rare and command a price premium

Cut
Mostly round or oval cabochon cut. Fine quality fire opals are facetted, although they are turbid rather than clear.

Mineral Deposits
Historically the main deposits were in Czechoslovakia, however since the early 1900's Australia has been the pre eminent producer of most of the world precious Opal. Currently about  85 percent of the world's supply of white precious opals is mined from the famous deposits at Lightning Ridge, White Cliffs, Coober Peddy and Andamooka.  Other deposits are found in Mexico, Brazil, Guatemala, Honduras, Indonesia, Russia and the United States.

Opal - Common Treatments
Opal are typically impregnated with oils, waxes, or plastics as part  a fracture filling enhancement. This markedly improves the appearance of the stone although over time the effect can be lost, and if the wax or oil decolours then some of the play of colour may be lost.

Important & Famous Opals
There are numerous examples of large Opal in existence, three of the largest ever discovered are, the " Andamooka Desert Flame" (6843kg), Big Ben" (4000 carats), and the "Light of the World" (2250 carats,

Opal - The Legend
According to the Aborigine legends, the creator came down to Earth riding on a rainbow, in order to bring the message of peace to all the mankind. Where his foot touched the ground, the stones became alive and started sparkling in all the colours of the rainbow. That was the birth of the opals.

Taken from:  www.touchstonegems.co.za

The allure of coloured gemstones in engagement rings

Fascination with coloured gemstones dates back to the very beginning of civilization. Long before the discovery of diamonds, the blue sapphire evoked visions of heaven; the red ruby was a reminder of the very essence of life. As early as Roman times, rings containing coloured gemstones were prized as symbols of power and friendship. In fact, the most powerful; and the most beloved, wore rings on every joint of every finger, reflecting the status of their position!

As Betrothal rings, coloured gemstones also hold an illustrious position. In addition to the beauty of particular colours, certain powers attributed to certain coloured gems made them not only beautiful but also meaningful choices. We see many examples of coloured gemstones in engagement and wedding rings, from many centuries ago to the present, used both alone and in combination with diamonds.

Following the discovery of diamonds in South Africa, which made diamonds more widely available and affordable, coloured gemstones were briefly ignored during the earlier part of this century. While there always has been people who preferred coloured gemstones despite the trends, coloured gemstone engagement rings have only recently re-emerged as a choice for the modern bride. The selection of a sapphire and diamond engagement ring by His Royal highness Prince Charles for lady Diana, followed not long thereafter by his brother Prince Andrew's selection of a ruby and diamond engagement ring for Sarah Ferguson, sparked a revival of interest in coloured gemstones for the bride to be.

While rubies, sapphires and emeralds have historically been among the most coveted gems, particularly for important occasions, there are many alternatives in coloured gems for today's bride, depending on budget and the personal connection to bride herself. Keep in mind that most birthstones come in several colours. You may be surprised to learn that the colour you associate with your birthstone may be only one of several colours in which the gemstone occurs.

For example, most people think garnet is dark red and are surprised to learn it can be emerald green, mandarin orange, yellow, white, purple; virtually every colour in the rainbow except blue. If you have discarded your birthstone as a choice because you don't care for its colour, check out all the colours in which it may be available before making a decision. Some colours in a particular gem may be rarer and less readily available and often costlier than better known colours, but the friendly staff at Touchstone Gems can work with you to discover your alternatives. One can combine a birthstone with diamonds, blending the symbolism of diamonds with the personal significance of the birthstone for a lovely, deeply meaningful, and often much more affordable ring.

In addition to birth gemstones, the choice of a particular coloured gemstone may be connected to mystical powers, attributes, or symbolism with which the gemstone has been historically identified. There is an almost limitless wealth of information about coloured gems, enough to stir the imagination of even the greatest cynic.

Love rings and "Sentimental" jewellery

Throughout history, coloured gemstones set in rings and other jewellery have carried hidden messages. We are seeing similar pieces being produced today. For example, a ring containing diamond, emerald, amethyst, ruby, emerald, sapphire, and topaz, arranged in that order, spells the word "dearest" if one takes the first letter of each word, thus carrying the sentiment that wearer is more dear than any other to the giver; a ring containing pearl, ruby, emerald, and sapphire spells "pres," which, in French, means "near" and suggests that the wearer is always near to the giver; amethyst, moonstone, opal, ruby, and emerald spells "amore," which is Italian for "love." And so on. Such a ring can create a wonderful, "sentimental" engagement ring.

Choosing the shape of a gemstone

Today's bride-to-be has more choices in engagement ring design and style than ever before. But the first step in creating the look you want is selecting the shape of the gemstone, a shape that is right for you. There are many shapes from which to choose, but it's important to choose the right shape because it will affect the overall design and look of your ring.

1. Round brilliant

2. Pear shape

3. Marquise shape

4. Oval shape

5. Octagon shape

6. Heart shape

7. Square shape

8. Baguette shape

9. Trillion Shape

Today, in addition to the classic shapes, there are many popular "fancy" shapes from which to choose.  Some of the new shapes lend themselves to very distinctive designs that would be difficult to create with other shapes; some exhibit unique personalities, not possible in any other; and some can even help you stay within your budget (some appear larger, for their weight, than traditional cuts, enabling you to get the size you want in a gemstone that actually weighs less than you might have thought you need). One of the most exciting parts of searching for your ring is discovering what is available today!

You should keep in mind, however, that fancy shapes, new and old, can be vary in their width and length, and in their basic proportioning, and these differences can result in a totally different look and feel on your hand. For example, an emerald cut gemstone that has a octagon shape will look very different from one that which is square; a broad shouldered pear shape might look too triangular for the hand, while one with softer, more rounded shoulders might be just what you want. To some extent, the choice of shape is a very personal matter, and there is no standard "ideal" range that is applied to shapes other than round, but you must be careful that the stone is not cut in such a way that is liveliness and brilliance is reduced or adversely affected.

As you begin to look at gemstones, try on all of the shapes; you may discover you like a shape you might not have considered otherwise! Try them in solitaire style and in designs that incorporate smaller gemstone accents. It won't be long before you have a clear idea of the shape that best suits your personal style and taste, the shape that you really like best.

Again, the use of side gemstones to accent a center stone (diamond or coloured gemstone), and the shape of the side stone, is a matter of personal choice. In addition to the shapes mentioned here, almost any of the other popular shapes can be found in small sizes and can be used to create an interesting and distinctive ring.

We would like to thank Bijan Aziz , the owner and Web Master for The Jewellery Hut for allowing us to use his copy on our website, in our blogs and newsletters.