August birthstone

August's main stone — the peridot

Iron does the colouring here, and that one fact explains the stone. In most gems the colour comes from a trace impurity, which is why corundum turns up red, blue, yellow and colourless; peridot is gem-quality olivine, and iron is part of the basic recipe rather than a contaminant. So peridot is green, has only ever been green, and cannot be anything else — there is no blue peridot, no pink one, and anyone offering you one is offering you something else.

Hold one over printed text with a loupe and look through the top facet. The edges of the back facets appear doubled, because olivine splits light strongly into two paths — a tell that green glass and green cubic zirconia cannot fake, since both show single crisp edges. Glass usually gives itself away anyway with round bubbles and a slightly soapy look; cubic zirconia goes the other way and sparkles far harder than any peridot ever has.

Softness is the catch nobody mentions. At around 6.5 to 7 on the hardness scale peridot scratches on ordinary dust, dislikes acid enough that years of sweat and the odd splash of lemon will dull the polish, and can crack outright from sudden temperature change — steam cleaning is a genuinely bad idea. Earrings and pendants stay beautiful for decades; a ring worn every day on a working hand will look tired within a few years.

The other stones listed for August

Sardonyx got the month first, long before peridot did, and for a strictly practical reason. It is banded chalcedony — reddish-brown sard layered with white — and warm sealing wax lets go of its polished surface instead of clinging, which made it the seal stone of the Roman world: an intaglio cut into those bands could be pressed into wax hundreds of times without ruining the carving. That is also why so much of the ancient carved gem material in museums is sardonyx rather than anything more glamorous. One caveat for buyers today: a great deal of the black onyx and banded sardonyx on sale is dyed agate, which is standard trade practice and not a scandal, but worth asking about.

The list keeps moving, and August moved most recently of all: in 2016 the American trade bodies added spinel as a third stone for the month, mainly because fine spinel had spent centuries being sold as ruby and finally deserved its own line. Our chart above keeps the two classics. And if the birthday falls from 23 August onward, the astrological tradition hands over an entirely different pair of stones — that reading lives on Virgo stones, and it does not overlap with this month's list at all.

What the peridot actually is

Zabargad, a bare hot island in the Red Sea now marked on charts as St John's, produced peridot for roughly three and a half thousand years, first for Egypt and later for Rome. Much of it travelled to Europe simply labelled emerald, and several celebrated medieval “emeralds” have since been identified as peridot — the great green stones on the Shrine of the Three Kings in Cologne Cathedral among them. Today the small commercial material mostly comes from San Carlos in Arizona, while the finest large crystals were found in the 1990s high in the Kohistan mountains of Pakistan.

Some peridot is not from this planet at all. Pallasite meteorites carry olivine crystals suspended in iron-nickel metal, a few of those crystals are clean enough to cut, and there is a small documented trade in extraterrestrial peridot — expensive, entirely genuine, and the only gem on this chart with that claim. Rather less exotic but useful in a shop: the old trade nickname for the stone is “evening emerald”, earned because its green holds up under lamplight where a real emerald tends to go flat and grey.

The August stone as a gift

Peridot is one of the few stones on this chart where a generous size is not a reckless decision — a clean two-carat stone is an ordinary present rather than an occasion, and size suits the mineral, because the green deepens as the crystal grows. Aim for a rich olive-to-grass green; the pale yellowish material is everywhere and cheap for a reason. Somewhere in the shop, though, a card will tell you the stone lifts the spirits or clears the mind. It does not, and the version of that promise that costs somebody something is the medical one, where a present gets treated as a reason to put off a doctor. Buy it because it is green under every lamp in the house.

Then let the softness decide the format. At 6.5 to 7 on the hardness scale peridot loses its polish to years of sweat, hairspray and the odd splash of lemon, and it can crack outright in a steam cleaner, so the money goes considerably further in earrings or a pendant than in a ring worn daily. If it has to be a ring, keep it for occasions and give it a bezel: a claw setting on a working hand is how a stone this soft ends up looking tired inside a couple of years.

Where the month chart came from

Nothing in geology or astronomy ties a mineral to a page of the calendar. The chart everyone quotes was agreed by American jewellers in 1912, in Kansas City, so that shops across the country would sell one list rather than twelve. It has been edited since: alexandrite, citrine, tourmaline and zircon were added in 1952, and tanzanite joined December as late as 2002 — thirty-five years after the stone was first dug up in Tanzania.

So when two shops give you two different stones, neither of them is lying. British lists keep bloodstone for March where American ones print aquamarine. June carries pearl from the old custom and moonstone plus alexandrite from the newer one. Read any of these charts as a custom with a paper trail — a dated commercial agreement — and not as a fact about the person born that month.

Month or star sign: two different lists

The month stone and the zodiac stone belong to different traditions: one is a jewellers' chart, the other is astrology, where the stone is derived from the ruling planet and the element. Two signs fall inside August: Leo stones (through August 22) and Virgo stones (from August 23). We do not repeat the astrology here — that reading lives on the sign pages.

At a glance

Frequently asked questions

The month-by-month chart is a 20th-century jewellery custom, not science: no link between a mineral and a birth date has ever been demonstrated. Stones do not heal and do not steer events — health questions belong with a doctor, not with a pendant. The stone images on this page are generated illustrations, not photographs of particular specimens.