June Birthstone: Alexandrite & Moonstone Jewelry

June has three recognised stones in the modern list: pearl, moonstone and alexandrite. It is the month with the widest choice.

This collection covers alexandrite and moonstone, which are very different from each other - one changes colour under different lighting, the other glows with a soft internal sheen.

None of the three is more correct than the others, so the choice can be made on colour, budget or simply what the recipient prefers.

Yes, and it is a real optical property rather than a trick of perception. In daylight alexandrite reads green to bluish-green; under incandescent light it shifts toward red or purplish-red.

The cause is chromium in the crystal, which absorbs light in a way that leaves two colour bands transmitting almost equally. Whichever the light source favours is the colour you see.

Strength of the change is the main measure of quality. A stone that shifts completely between the two is far more desirable than one that shifts only partially.

Yes. Laboratory-grown alexandrite is the same mineral as natural alexandrite - the same chrysoberyl, the same chemistry, the same genuine colour change. It is not a simulant.

The difference is where the crystal formed. Growth in controlled conditions means the material is consistent and available in sizes that natural alexandrite rarely reaches.

This matters practically because natural alexandrite with a strong colour change is among the rarest gemstones there is. Each listing states which the piece uses.

The effect is called adularescence, and it comes from the stone's internal structure. Alternating microscopic layers of two feldspar minerals scatter light and send it back as a soft sheen that appears to float beneath the surface.

Because the glow moves as the stone moves, it reads as light travelling inside the stone rather than reflecting off it.

Rainbow moonstone shows flashes of additional colours alongside the characteristic blue. The finest material combines a clear body with a strong, mobile sheen.

Because facets would work against the effect. Faceting returns light from flat surfaces, and moonstone's appeal comes from light scattering deep inside the stone.

A smooth polished dome lets light enter, scatter through the internal layers and come back as the floating sheen. The dome is what makes the glow visible.

Orientation matters too - the effect only appears along one axis of the crystal, so the cutter must position the stone correctly for it to show at all.

It is not the ideal everyday stone. Moonstone sits around 6 to 6.5 on the Mohs scale, and more importantly it has a distinct cleavage direction, so a sharp knock can split it regardless of surface hardness.

A bezel setting protects it considerably, which is why so many moonstone designs use one, and a low profile helps too.

As a pendant or earrings, moonstone is entirely practical - those pieces take a fraction of the impact a ring on a hand does.

Alexandrite, by a wide margin. It is chrysoberyl at 8.5 on the Mohs scale, which puts it above every common coloured stone except sapphire and ruby.

That makes alexandrite entirely suitable for a ring worn every day, including an engagement ring.

Moonstone at 6 to 6.5 with a cleavage direction is the more delicate of the two and belongs in pieces that take less impact. Both are correct for June; they just suit different kinds of jewellery.

Rainbow moonstone shows flashes of colour beyond the characteristic blue - hints of orange, green or violet moving across the stone alongside the sheen.

It is technically a labradorite rather than the adularia feldspar of classic moonstone, though it is sold and worn as moonstone and shows a comparable floating glow.

It tends to be more transparent than traditional moonstone, and the multicoloured flashes give it more visual movement. Care requirements are the same.

White gold and platinum keep alexandrite's colour change readable by giving it a neutral background, and they suit moonstone's cool blue sheen very naturally.

Yellow gold warms both stones. With moonstone it produces a softer, more antique look that many people prefer; with alexandrite it adds warmth that can favour the red phase.

Rose gold is a striking contrast against moonstone's blue in particular. It is worth looking at the same design in more than one colour, since these stones respond to their setting more than most.

Alexandrite is straightforward - warm water, mild soap and a soft brush, rinsed and dried with a soft cloth.

Moonstone needs more care. Warm soapy water and a soft cloth only, and never an ultrasonic or steam cleaner: the vibration and the heat are both genuine risks to a stone with a cleavage direction.

Keep both away from household cleaning chemicals, and store moonstone where nothing harder can rest against it.