Moonstone and alexandrite, with pearl on the older lists. June is one of the few months with a genuine choice.

Pearl is the traditional stone and goes back centuries. Moonstone was added to the modern list in 1912. Alexandrite joined later, after it was discovered in Russia in the 1830s and turned out to be rare enough to be worth having. All three are correct — you pick the one you like.

Ours is lab-created, and we'd rather say so. Natural alexandrite is one of the rarest gems on earth — a stone large enough for a ring costs more than most cars. Lab-created alexandrite is the same mineral with the same chemistry, grown rather than mined, and it performs the same trick: green in daylight, red under lamplight.

The effect is called adularescence, and it comes from the stone's structure rather than anything on the surface. Moonstone forms in microscopic layers of two feldspars, and light scatters between them — which is why the glow moves as you tilt the stone instead of sitting still.

Moonstone is tied to intuition and to cycles, which is why it's long been associated with the moon. Alexandrite, changing colour as the light changes, is associated with adaptability.

It's softer than most gemstones — 6 to 6.5 on the Mohs scale, below quartz — and it has natural cleavage planes, so it wants more care than a garnet or a topaz. Keep it away from knocks and abrasive surfaces and it lasts indefinitely.