The Alexandrite Engagement Ring: A Complete Australian Guide

What is an alexandrite engagement ring?

An alexandrite engagement ring is set with alexandrite, the colour-change variety of the mineral chrysoberyl. In daylight it looks bluish-green to green; under warm incandescent light or candlelight it turns purplish-red to raspberry. That shift, called the colour change, is the defining feature of the stone and the main thing you pay for.

Chrysoberyl is beryllium aluminium oxide, BeAl₂O₄, and alexandrite gets its colour from small amounts of chromium replacing some of the aluminium. Our guide to the chemical make-up of diamonds, sapphires and other gems puts this in context. Alexandrite is the modern June birthstone alongside pearl and moonstone, and of the three it is the only one hard enough for a ring worn every day.

The first stones were found in Russia's Ural Mountains in the 1830s and, according to the usual story, were named after the future Tsar Alexander II. The Russian deposits are largely worked out, so most alexandrite sold today comes from Brazil, Sri Lanka, India and East Africa. Clean natural stones over a carat with a strong change are genuinely rare, which is why alexandrite sits among the most expensive coloured gemstones per carat.

If any of these terms are new, our explainer on hardness, refractive index and specific gravity walks through each one.

Why does alexandrite change colour?

Chromium in alexandrite absorbs light strongly in the yellow part of the spectrum and in the violet. That leaves two 'windows' where light passes through: one in the blue-green and one in the red. The two windows are almost evenly balanced, so the colour you see depends on which one the light source feeds more.

• Daylight and cool white LED: rich in blue and green, so the stone looks green to bluish-green.
• Incandescent globes and candlelight: rich in red and yellow, so the stone looks red to purplish-red.
• Warm LED (around 2700 K) and mixed light: sits in between, often giving a purple-grey or brownish look. This is normal, not a fault.

Alexandrite is also strongly pleochroic, meaning it shows different colours along different crystal directions: green, orange-yellow and purplish-red. A skilled cutter orients the rough so the face-up colour is green-to-red rather than orange, sometimes at the cost of weight. That is one reason fine alexandrite is often cut as an oval or cushion with a slightly irregular outline.

Alexandrite is not the only gem that does this. Some colour-change garnet and sapphire show a similar shift naturally, and several man-made gemstones are produced specifically to imitate the effect, which matters when you are checking a stone.

Is an alexandrite engagement ring durable enough for everyday wear?

Yes. Hardness is resistance to scratching, and at 8.5 on the Mohs hardness scale alexandrite sits well above household dust (mostly quartz, around 7), which is what slowly dulls softer gems. Toughness is resistance to chipping and breaking, and chrysoberyl rates good to excellent, with only weak cleavage. It is stable in normal light and heat, so it will not fade.

In practice, an alexandrite ring behaves much like a sapphire: it can take years of wear, but a hard knock on a tiled bench can still chip an edge. Our guide to gemstones that stand up to daily wear compares the options, and ruby engagement rings are worth a look if you want a red stone with slightly more toughness.

How is alexandrite quality judged?

For most gems, colour comes first. For alexandrite, the strength of the colour change comes first, then how attractive each of the two colours is, then clarity, cut and size. Labs and dealers usually describe the change in words, and the trade often adds an estimated percentage.

• Colours: a bluish-green to emerald-green by day and a raspberry to purplish-red by night are most valued. Olive, yellowish or brownish tones lower the price.
• Clarity: alexandrite commonly has fingerprints, fine needles, growth tubes and twinning lines. Aim for eye-clean (no inclusions visible at normal viewing distance); loupe-clean natural stones are scarce.
• Cut: usually a mixed cut (brilliant-style crown, step-cut pavilion). Check for a 'window', a washed-out centre where light passes straight through.
• Size: most natural alexandrite is under 1 carat. Prices per carat climb steeply above 1 carat, and again above 2 carats.

Alexandrite is generally not heat treated, which sets it apart from most sapphire and ruby; our guide to heated and unheated stones explains why that matters for other gems. Occasionally surface-reaching fractures are filled with oil or resin to improve clarity. Ask for a report if the price suggests an exceptional stone, and see how fracture filling works for what to look for.

Where does alexandrite come from?

Origin affects the colour character and, for some sources, the price. Laboratories such as GIA, SSEF and Gübelin can give an origin opinion for natural alexandrite, though not every stone can be traced.

Australia is not a commercial source of alexandrite. Our sapphire fields in Queensland and New South Wales produce corundum, and chrysoberyl turns up only in minor amounts. So an alexandrite in an Australian shop has almost always been imported, which is another reason to ask about its source and paperwork.

Natural vs lab-created alexandrite: how can you tell the difference?

There are three things sold as 'alexandrite', and they are very different in value:

• Natural alexandrite: mined chrysoberyl with a colour change.
• Lab-created (synthetic) alexandrite: real chrysoberyl grown in a laboratory, with the same chemistry, hardness and colour change. It has been produced commercially since the 1970s by flux growth, Czochralski pulling and other methods.
• Simulants: different materials that imitate the colour change, mainly synthetic colour-change corundum (vanadium-doped), synthetic colour-change spinel and glass. These have been sold to travellers as 'alexandrite' for decades.

Separating natural from lab-created alexandrite usually needs a gemmological laboratory, because the two share the same properties. Simulants are easier: a refractometer reading above 1.76, or a stone that is singly refractive, rules out alexandrite. The same synthetic colour-change corundum is the same mineral as sapphire and natural ruby, just grown in a lab with vanadium.

Both natural and lab-created alexandrite make a hard-wearing ring. Lab-created stones offer a strong change at a fraction of the price; natural stones are rarer, and each carries its own inclusions and origin. Our guide to choosing between natural and lab-created gems for an engagement ring sets out the trade-offs. Whichever you choose, the seller should disclose it clearly in writing.

How much does an alexandrite engagement ring cost in Australia?

Alexandrite pricing has a wider spread than almost any other gem, because the strength of the colour change and the size both multiply the price. These are approximate loose-stone ranges; a specific stone can sit outside them.

On top of the stone, a solid gold or platinum setting typically adds roughly AUD 2,000–6,000, depending on metal, design and how many diamonds are used. For comparison, a 1 carat fine natural alexandrite usually costs more than a sapphire of similar quality and size, and can overlap with fine ruby. If the colour change matters less to you than a particular colour, it is worth looking at other coloured gems we work with too.

Which settings and metals suit an alexandrite ring?

The metal you choose nudges which colour you notice. White gold and platinum keep the daytime green crisp and cool. Yellow gold warms the stone and flatters its evening red but can make a weaker green look olive. Rose gold sits in between and suits stones with a purplish-red change.

• Four or six claws: shows the most of the stone and lets light in from the sides, which helps the colour change. Six claws suit rounds and cushions; four suit ovals.
• Bezel or half-bezel: a rim of metal around the edge; very secure for active hands and protects the girdle from chips.
• Diamond halo: white diamonds frame the stone and give a neutral reference, so both colours read more clearly. It also adds apparent size, useful because many natural alexandrites are under 1 carat.
• Three-stone: alexandrite centre with white diamonds either side, or alexandrite side stones beside a diamond.

Because alexandrite is often cut to an irregular outline to save colour and weight, a setting made to the stone's exact measurements sits better than an off-the-shelf head. If you like the idea of a ring with two colours that never changes with the light, a parti sapphire is the closest alternative.

How do you clean and care for an alexandrite ring?

• Everyday cleaning: warm water, a drop of mild dishwashing liquid and a soft toothbrush, especially under the stone where soap and lotion collect.
• Ultrasonic and steam: usually safe for untreated alexandrite without fractures. Avoid both if the stone has surface-reaching fractures or any filling.
• Knocks: take it off for gardening, gym weights and heavy lifting; a hard blow can chip even a tough stone.
• Chemicals: chlorine in pools and spas will not harm the stone but can weaken gold alloys over time.
• Checks: have the claws checked about once a year; worn claws are the most common reason any stone is lost.

Unsure of a word on a valuation or report? Our jewellery glossary explains the common terms.

How to choose an alexandrite engagement ring: step by step

1. Decide natural or lab-created. Both are true chrysoberyl. Set your budget first, because natural prices climb steeply with size and colour change.
2. See the stone in two lights. Look at it in daylight or a daylight-balanced lamp, then under an incandescent globe or candle. Judge the change for yourself; read up on what makes a colour change strong or weak first.
3. Check the colours, not just the change. Aim for a clear green and a clear red or purplish-red, with as little brown or grey as possible.
4. Ask for identification. For a natural stone of any real value, ask for a laboratory report confirming natural alexandrite, any treatment and, if it matters to you, the origin.
5. Look for eye-clean clarity and a lively cut. No visible inclusions at arm's length and no washed-out window in the centre.
6. Choose a setting that protects the edge. Claws or a bezel in a metal that suits the colour you care about most.