ADV Education

Australian Sapphire Guide

Sapphires, among the world’s oldest gemstones, trace their origins back billions of years. These noble gems reflect the untamed beauty of the Australian wilderness, sourced from the ancient landscapes of the New England Fields in northern New South Wales and the gently rolling hills of Central Queensland.

With a colour palette ranging from oceanic blues and forest greens to wattle yellows and mesmerising parti tones, Australian sapphires boast an unparalleled variety.

Quick Facts about Australian Sapphires

Hardness

Australian sapphires rank 9 on the Mohs scale of hardness, second only to diamonds. This high hardness makes them resistant to scratching and enables a beautiful, lasting polish. These gems are also highly durable, with excellent resistance to chipping and sudden temperature changes.

Volcanic Origins

Unlike their Sri Lankan and Burmese counterparts, which form in metamorphic environments, Australian sapphires are born from volcanic activity. These gems crystallise from mineral-rich lavas produced by ancient volcanic eruptions.

Composed of Corundum

All sapphires, including Australian ones, are made of crystalline aluminium oxide, also known as corundum (Al₂O₃). With a specific gravity of 3.9–4, they are prized for their durability and beauty.

What Makes Australian Sapphires Special?

On the eastern side of Australia, Tertiary volcanic deposits—dating back up to 40 million years—serve as the primary source of these gems. While sapphire deposits are found near these volcanic regions, only a few areas yield stones in quantities large enough for commercial mining.

Key Mining Regions

• New South Wales: The New England district near Inverell and Glen Innes.
• Queensland: The Anakie Gemfields, near the towns of Sapphire and Rubyvale, west of Emerald.

The Beauty of Colour Banding in Australian Sapphires

Australian sapphires are renowned for their distinct colour banding, where zones of blue, green, and yellow appear in harmonious patterns. This natural feature often allows for the cutting of stunning bi-colour or parti sapphires.

• Parti Sapphires: These feature distinct bands of blue, green, and yellow. The rarest specimens display all three colours.
• Teal Sapphires: These showcase a captivating blend of blue and green, with flashes of each colour depending on the light.

The intricate trigonal crystalline structure of Australian sapphires results in their uniquely varied and vibrant colours, making them some of the most fascinating gemstones in the world.

Main Colours of Australian Sapphires

Blue

The most common colour, comprising 80% of Australian sapphires. Variations include Cornflower, Royal, Midnight, Steel, and Indigo, with their vibrancy influenced by iron (Fe) content.

Green

Green sapphires are a rare and prized blend of blue and yellow, with their depth of colour depending on iron concentration. Darker greens are particularly valuable.

Yellow

Bright and radiant, yellow sapphires owe their colour to iron ions (Fe³⁺). Higher concentrations can produce golden hues, while the addition of magnesium (Mg) creates stunning orange tones.

Parti Sapphires

Featuring a mix of blue, green, and yellow, Australian parti sapphires are globally unique. Their distinct banding ensures that no two stones are alike, enhancing their allure and value.

Teal Sapphires

Teal sapphires, with their exquisite fusion of blue and green, are becoming increasingly sought after. Australia is the leading producer of these gems, setting global trends with their vibrant and distinctive hues.

Australian sapphires are a testament to the continent’s ancient geology and unparalleled natural beauty. From their remarkable durability to their unique colour combinations, these gemstones are a treasured symbol of the Australian landscape and heritage.

The Birth of Opal

Precious opals were formed in the distant geological past when an inland sea covered much of the eastern half of the Australian continent. During the Cretaceous period, dinosaurs roamed the shallow seas, and their remnants are now fossilised in the outback. Remarkably, some of these dinosaur fossils have transformed into precious opal, making opalised fossils a unique and significant part of Australia’s natural history.

Australia's Indigenous landowners spoke of opals in their Dreamtime legends of creation. It is easy to see why, in some Aboriginal folklore, opals are associated with the rainbow, the Rainbow Serpent, and Dreamtime spirits and creators.

European history also illustrates the enduring allure of opals. The famous Nonius Stone, owned by the Roman senator Nonius, was so cherished that he refused to sell it to Mark Antony, who had desired it for Cleopatra. In his Roman treatise on gemstones, Natural History, Pliny the Elder praised opals with one of the earliest and finest descriptions: “In opal, you will see the splendour and brilliant fire of ruby, the glorious purple of amethyst, the sea-green of emerald—all these colours glittering together in an incredible way.”

Today, opals are mined in three Australian states: New South Wales, Queensland, and South Australia. Lightning Ridge, NSW, is world-renowned for its exquisite Black Opals and fine Crystal Opals. Boulder Opals from Queensland captivate with their complexity and brilliance, while Andamooka and Coober Pedy in South Australia yield some of the finest Crystal and White Opals.

Australian history also celebrates Tully Wollaston, a pioneer of the opal trade. In the late 19th century, Wollaston travelled through the outback, trading opals and documenting his adventures, cementing his place as the father of Australia’s opal industry.

Precious opal is, without doubt, Australia’s national gemstone. Black Opal serves as the state gemstone emblem of New South Wales, while South Australia honours precious opal as its state gemstone.

Factors Determining the Value of Opals

The value of an opal is determined by several key factors:

• Brilliance: The brightness of an opal’s play-of-colour is paramount; higher brightness translates to higher value.
• Darkness: A black or dark background enhances the play-of-colour, contributing significantly to an opal’s value.
• Pattern: Unique patterns, combined with brilliance, can dramatically increase value.
• Colours: The number and vibrancy of colours affect value. While red hues are often the most sought after, brilliance and pattern remain more critical.
• Shape: Cabochons with high domes are generally more valuable than flatter stones. Freeform shapes, often seen in Boulder Opals, lend themselves to unique jewellery designs.
• Inclusions: Natural inclusions may reduce value, but some irregularities, like sand in the back of the stone, can assist in identification without significantly affecting value.

Types of Opal

Natural Australian precious opals are categorised by type and body tone:

• Black Opal: Found primarily in Lightning Ridge (NSW), these opals display vivid play-of-colour against a black body tone, making them rare and highly prized.
• Crystal Opal: Translucent or transparent, with brilliant colours that appear to come from deep within the stone. Found across Australian fields.
• Boulder Opal: Naturally attached to its ironstone host rock, Boulder Opals are known for their stunning colours and patterns, often rivaling Black Opals in brilliance.
• Matrix Opal: A unique form where opal is intricately diffused within the host rock, often ironstone or sandstone.

Other types include composite opals like doublets and triplets, as well as synthetic and imitation varieties.

Caring for Your Opal

Opals, while durable, require proper care to maintain their beauty:

• Natural Opals: Clean gently with a soft toothbrush and mild detergent. Avoid harsh chemicals or ultrasonic cleaners.
• Doublets and Triplets: Prolonged water exposure can cause separation of layers; clean with a damp cloth instead.
• Storage: Store opals in padded cloth bags. For extended periods, wrap them in cotton wool with a few drops of water in a sealed plastic bag to prevent drying out.

The Argyle Pink Colour Chart was created by Argyle to grade the different shades, tones and saturations of Argyle pink diamonds accurately. It is found on Argyle Certificates, on Argyle parcel papers and reproduced on third party seller certificates. The grading system can be used in addition to the Gemological Institute of America's (GIA) fancy coloured diamond grading system.

Please note, the Argyle Pink Diamonds Colour Chart is applied exclusively to Argyle diamonds, it is not to be used for pink diamonds found at locations outside of the Argyle mine.

The Pink Colours

The chart has 3 pink colours - Pink, Pink Rose and Purplish Pink. 

Pink (P) is also known as a 'straight pink'. This is a pink colour that is considered a 'classic' pink colour.

Pink Rose (PR) is a newer colour classification, it replaced the former colour 'brown pink'. It is a pink colour that has more of a brownish, antique, dusky pink look. It is usually priced lower than the pink colour.

Purplish Pink (PP) is a pink with purple overtones. It is the most prized and can fetch higher prices than the Pink (P) colour.

The Saturation

The chart has 9 saturations - 1 is the most saturated (a very deep/vivid/intense colour) through to 9 which is the least saturated (a very light/faint colour). After 9, the colour is considered white or near colourless/colourless.

The Other Argyle Colours

Over the years the colour chart has expanded to include other colours. Although still referred to as the Argyle Pink Diamond Colour Chart, it now includes Blues, Reds, Near Colourless and Pink Champagnes.

Blue Violet (BL) is blue with tones of violet and grey. Argyle blues are known for their earthy, greyish blue colour. 

The Blue grades have 3 saturation levels. It is in reverse order to the Pink colour. It begins with the least saturated BL1 through to BL3. Higher saturation than BL3 is BL3+ (Blue 3 plus). There is no BL4.

Red (R) and Purple Red (pR) are the colour grades for the very rare red Argyle diamonds. Red is a 'straight red' and Purple Red is a red with purple overtones.

Near Colourless (NCL), Near Colourless Pink (NCP), Colourless Pink (CP), Colourless Pink Equivalent (CPE) are newer colour grades that were added later to the chart. These grades are classified as lighter/fainter than the 9P grades but not considered white or colourless. They have faint pinkish, brownish or yellowish overtones. These grades do not have saturation numbers.

Pink Champagne (PC) are champagne diamonds with pinkish overtones. The colour can be described as pinkish-orangey-brownish. The Pink Champagne grades have 3 saturation levels. PC1 through to PC3. 1 is the least saturated and 3 the most saturated.

Discontinued Argyle Colours

Brown Pink (BP) colour grade was replaced with the Pink Rose (PR) colour grade. Brown Pink is no longer used but can be found on earlier Argyle certificates. (An unverified story is that the Pink Rose grade replaced Brown Pink because it sounded more favourable.)

Argyle Champagnes, Cognacs, Yellows & Whites

Champagne Cognac (CC), Fancy Yellow (FY) and White are also colours of diamonds mined at Argyle. They do not have their own colour chart created by Argyle. Their colour grades are based on the Gemological Institute of America (GIA) fancy colour diamond chart.