Collection: October Birthstone Jewelry

Why opal flashes

Opal's colour is not pigment. It is structure. The stone is made of microscopic silica spheres stacked in a regular grid, and when those spheres happen to be the right size and evenly enough arranged, they split light the way a prism does. That is the play of colour, and it is why an opal shifts as you move rather than sitting at one shade.

It also explains the difference between the two things people call opal. Precious opal has that ordered structure and flashes. Common opal does not, and comes as a solid milky or honey-coloured stone. Both are genuine opal; only one puts on a show.

Opal is also unusual in holding water — typically 3 to 10 percent by weight, sometimes more. That is central to how it has to be looked after, and it is the reason opal has a reputation for being fragile that it partly deserves.

Tourmaline, the gem that couldn't decide

Tourmaline has the widest colour range of any gemstone family. Pink, red, green, blue, black, colourless, and crystals that run through two or three shades in a single piece — watermelon tourmaline, pink core with a green rim, is the famous one. For centuries it was routinely mistaken for other stones entirely; a good deal of what was catalogued as ruby or emerald in old European collections turned out to be tourmaline.

Black tourmaline is the one most people meet first, and it does different work from the coloured varieties. It is the grounding, boundary-setting stone — the one people reach for when other people's moods keep arriving uninvited. Pink tourmaline sits at the heart, green at the heart in its more expansive register.

What October's stones are for

Opal is worn for creativity and emotional honesty, and it has an old reputation as an amplifier — it does not add a mood so much as turn up whatever is already there. Tourmaline is the transformation and protection side. Between them October covers change and the ability to stay yourself through it, which is a reasonable summary of the month itself. The October opal and tourmaline guide covers the meanings in more detail.

Genuine stone, lab-created and opal glass

Opal is one of the most widely imitated stones there is. Lab-created opal exists and is genuine silica with the same structure, grown rather than mined. Opalite is a glass — a manufactured material with a soft blue-white glow that looks like opal and is not. Both are perfectly good things to wear; neither is opal in the geological sense.

Every listing here states what it is: genuine opal, lab-created opal, opalite or glass. Nothing is described as opal unless it is.

Opal needs the gentlest routine on the site

Opal is 5.5 to 6.5 on Mohs, soft, and holds water inside it. Sudden dryness or a sharp temperature change can craze it — fine surface cracking that cannot be undone. Never use an ultrasonic or steam cleaner. Do not store it somewhere very dry or very hot. Do not soak it, particularly if it is a doublet or triplet, where water gets into the glue layer.

Warm water, mild soap, soft cloth, dry properly, and take it off before anything physical. Tourmaline is far tougher at 7 to 7.5 but still dislikes hard knocks and sudden heat. Full routine in the crystal care guide.

Wearing it

Opal picks up whatever is near it, so the setting metal genuinely changes the stone: silver pulls out the blues and greens, gold brings up the warm oranges and pinks. It looks best against neutral clothing where nothing competes with the flash.

Black tourmaline is the opposite — it absorbs rather than reflects, and reads as a matte anchor. It works well as the darkest point in a stack of lighter stones. For an October birthday, pendants and earrings are kinder to opal than rings.