August's birthstone is peridot — and it is the only gem on the list that arrives on earth two ways: pushed up out of volcanoes, and dropped out of the sky inside meteorites.
August also has spinel and sardonyx on the modern list, which most people have never been told. Peridot is the one that matters, and it has the better story.
The stone with only one colour
Almost every gem comes in a range. Sapphire is blue, pink, yellow, green, colourless. Tourmaline does nearly everything. Quartz alone accounts for amethyst, citrine and rose quartz.
Peridot is green. That is the entire range — from a yellowish olive to a deep grass green, and nothing else, ever.
The reason is structural. Peridot is gem-quality olivine, and the green comes from iron that is part of the mineral's own chemistry rather than a trace impurity that happens to have wandered in. In most coloured stones the colour is an accident. In peridot the colour is the mineral. You cannot have olivine without it.
This also means peridot is never heat-treated, irradiated or dyed, because there would be no point. Whatever colour it has, it grew with. Among coloured gemstones that is genuinely unusual.
Mined at night on an island in the Red Sea
The oldest known source is Zabargad, a small island in the Red Sea off the Egyptian coast, worked for something like three and a half thousand years. The ancient name for the material was topazios — which is why old texts describing "topaz" are frequently describing peridot, and why the two stones have been quietly confused with each other since antiquity.
The miners on Zabargad worked at night. The usual explanation given is that peridot is very hard to spot in daylight glare against the rock, and easier to find by lamplight, when it catches the flame. Whether that is the whole reason or a good story attached afterwards, the night working is in the record.
It has long been argued that a good number of Cleopatra's famous emeralds were, in fact, peridot from that island. There were no emerald deposits producing at that scale nearby. There was Zabargad.
The one that comes from space
Olivine is not rare in the universe. It is a major component of the earth's upper mantle, and it turns up in pallasite meteorites — a class of meteorite made of iron-nickel metal with olivine crystals suspended in it, thought to come from the boundary between the core and mantle of a shattered protoplanet.
Some of those crystals are gem quality. They are cut and sold as peridot, and they are older than the earth. Not a marketing line: the parent bodies formed in the first few million years of the solar system.
Closer to home, there is a beach in Hawaii — Papakōlea — where the sand is green because it is largely olivine weathered out of the surrounding volcanic rock. Peridot from volcanoes and peridot from space are the same mineral.
Wearing it
Peridot sits around 6.5 to 7 on the Mohs scale. That is solid enough for a ring worn regularly, but not diamond-hard, and it does not enjoy sharp knocks — olivine has directions along which it parts more easily than others. Warm soapy water and a soft brush; no ultrasonic cleaner.
Its other quality is what happens under artificial light. Peridot holds its green under lamplight where a lot of green stones go grey or brown. Jewellers used to call it the evening emerald for exactly that reason.
What we make for August
Peridot appears in The Garden Rule, a multi-stone ring where it sits with amethyst and topaz — three stones that have no business agreeing with each other and do.
The everyday version is Month in Colour: one baguette stone on a fine chain, solid 925 sterling silver plated in gold rather than plated brass, so that when the plating eventually wears, what is underneath is silver. The August stone is olive. It is cubic zirconia cut to the birthstone colour, not natural peridot. We put that on the product page, not in the small print.
Made after you order, so allow up to ten days.
All twelve months, and what each stone actually is →
Where stone meanings actually come from →
A birthstone is a date, not a diagnosis. Nothing here treats, prevents or cures anything.