Birthstones for September and October
In the fifth of our six-part birthstone series, ADORN spotlights the gems for those born in the months of September and October.
Sapphires, the birthstone for people born in September, in the medieval ages came to symbolise the heavens because they are found in various shades of blue replicating the colours of the skies. Sapphires are linked to faithfulness and integrity and it is for this reason that many brides in the Western world prefer sapphires on their engagement rings.
The opal gemstone for the October-born often showcases a play-of-colour. Opal gets its name from the latin word ‘opalus’, derived, in turn, from the greek ‘opalios’, which has its origins in the Sanskrit word ‘upala’ or precious. Considered to bestow the power of foresight to its wearers, opals are also believed to offer protection against diseases.
The Gemological Institute of America (GIA), gives you inputs about these two amazing and intriguing stones.
Sapphire: The King of Blue
Did You Know?
Blue sapphire’s hues reflect the sky’s every shade, from blazing afternoon to velvety midnight. Its extraordinary colour is the standard against which other blue gems – from topaz to tanzanite – are measured.
Sapphire, like ruby, belongs to the mineral species corundum. Most jewellery customers think all sapphires are blue; however, sapphire comes in many colours. When gem and jewellery professionals use the word “sapphire” alone, they normally mean blue sapphire. Other colours, such as yellow, pink and orange, are termed “fancy sapphires”.
Both blue and fancy sapphires come from a variety of sources including Madagascar, Tanzania, Sri Lanka, Myanmar and Australia.
History and Lore
Traditionally, sapphire symbolises nobility, truth, sincerity and faithfulness. For centuries, this gem has been associated with royalty and romance. Ancient Greeks and Romans were convinced that blue sapphires protected them from envy and harm.
The 4C’s : Clarity, Colour, Cut and Carat Weight
The most highly valued sapphires are velvety blue to violetish blue, in medium to medium-dark tones with strong to vivid saturation. The saturation should be as strong as possible without darkening the tone and compromising the brilliance. Sapphires with these qualities command the highest prices per carat.
Blue sapphires typically have some inclusions, but they generally have better clarity than rubies. Blue sapphires with extremely high clarity are rare, and very valuable. Generally, inclusions make a stone less valuable, and the price can drop substantially if the inclusions threaten the stone’s durability. But some inclusions in sapphires can actually increase the value of the gemstone, such as some of the most valuable Kashmir sapphires, which contain tiny inclusions that give them a velvety appearance.
Fashioned sapphires appear most commonly in traditional pear, round, oval, cushion and emerald cuts with brilliant-cut crowns and step-cut pavilions. Cutters focus on factors like colour zoning, pleochroism, and the lightness or darkness of a stone to achieve the best overall colour, maintain the best proportions and retain the most weight possible.
Blue sapphires can range in size anywhere from a few points to hundreds of carats, and large blue sapphires are more readily available than large rubies.
Many sapphires are treated in some way. Heating and lattice diffusion are the most common treatments. Other treatments – including facture-filling, coating and dyeing – are not as common. It’s important to ask whether the stone you are considering has been treated.The price per carat for fine-quality, untreated stones can be considerably higher because of their scarcity.
How to Care for Sapphire
Sapphire, a 9 on the Mohs scale for gauging mineral hardness, is a great choice for daily jewellery. Sapphire can be cleaned in an ultrasonic cleaner or steamed, but this should only be done by a professional jeweller after a close inspection to determine if any fillers or dyes are present. As with most gemstones, a soft moistened cloth or a soft bristle toothbrush can be used with mild soap and water to clean the gem.
Opal: A Kaleidoscope of Flashing Rainbow Colours
Did You Know?
Known for its shifting play of kaleidoscopic colours, opal can display all the colours of the rainbow. No other gem duplicates opal’s combination of colour and phenomenon – especially when the colours in the gem change or appear to change depending upon the light.
Opal forms when water from seasonal rains soak deep into underground rock, carrying dissolved silica (a compound of silicon and oxygen) downwards. During dry periods, much of the water evaporates, leaving a solid deposit of silica – opal – in the cracks and between the layers of sedimentary rock. Opal contains a significant amount of water, usually about 3-10%, but it can be as much as 20% in some types.
Experts divide opal into many different categories, but the main types are white, crystal or water, black, fire and boulder opal. Australia is the largest source of opal and remains a major source of black, white and boulder opal. Ethiopia is another significant source of opal, with less-plentiful sources in Brazil, Canada (British Columbia), Honduras and the U.S. (Idaho, Nevada and Oregon). Mexico produces almost all of the world’s fire opal.
History and Lore
Ancient Romans called it opalus, or “precious stone,” and believed it symbolised love and hope. The Bedouin believed opals contained lightning and fell from the sky during thunderstorms. Arabic legends say it falls from the heavens in flashes of lightning. The ancient Greeks believed opals gave their owners the gift of prophecy and guarded them from disease. Europeans have long considered the gem a symbol of hope, purity and truth.
The 4C’s : Clarity, Colour, Cut and Carat Weight
An opal might display a single colour, two or three colours, or all of the colours of the rainbow. Opal displays background colour – also called body colour – in addition to play-of-colour.
Some background colours tend to be more prized than others. All other quality factors being equal, many buyers favour black because play-of-colour tends to stand out attractively against a dark background.
Opal’s play-of-colour must be vivid and bright to command a high rating. If it is not just bright, but also ranges across the entire colour spectrum, it’s very rare and valuable.Traditionally, red is considered the best in play-of-colour, orange the next most desirable, followed by green. Favoured colours can vary with fashion or personal preference, however. The most valuable opals display play- of-colour from all angles.
Pattern describes the arrangement of an opal’s play- of-colour. Connoisseurs generally prefer large, closely arranged patches of colour over tiny, scattered dots.
With an opal, clarity is its degree of transparency and freedom from inclusions. Opals, like other gems, can have fractures, or pits and other surface blemishes. An opal might also contain fragments of its host rock, called matrix.
The cutter considers an opal’s colour, pattern and clarity when planning the finished gem. Opal cutters usually cut top-quality rough to show off its spectacular play-of-colour.
Opals come in a wide range of sizes and carat weights. It has relatively low density compared to many other gemstones so even larger sizes can be comfortable to wear.
If an opal loses moisture, it can lead to crazing – a fine network of cracks that resembles a spider’s web. The moisture loss can be caused by heat or excessive dryness, or by exposure to bright light or direct sunlight.
Opals can be treated to make them more attractive and marketable; synthetic and imitation materials are also available as options to natural opal. Sellers must provide full disclosure, and consumers should always ask about treatments and the nature of the material before purchasing.
How to Care for Opal
Opal, a 5 to 6.5 on the Mohs scale of mineral hardness, is delicate and needs to be treated gently to last a lifetime. Sudden changes in temperature may cause opals to crack or fracture. Some gemmologists advise storing opal in a damp environment to avoid crazing. Clean opal jewellery with a dampened, soft fabric or a soft bristle toothbrush doused in water. Never use abrasive or chemical cleaners on opal, and avoid ultrasonic or steam cleaners.