August Birthstone
August's headline stone is peridot — one of the few gems that comes in exactly one color, an unmistakable olive-to-lime green. Alongside it sit spinel, the most underrated fine gem in the trade and the newest addition to any month's list (2016), and sardonyx, the banded red-and-white stone of ancient signet rings that held August's spot for centuries.
That makes August a three-stone month with three eras in it: an antique carving stone, a volcanic green gem the Egyptians mined on a Red Sea island, and a modern connoisseur's stone finally given official status. Here is what each one is, what color August claims, and what to know before buying.
The August birthstones
Gem-quality olivine, a magnesium iron silicate formed deep in the Earth's mantle and carried up by volcanoes — some peridot even arrives inside pallasite meteorites. It is idiochromatic: iron is part of its formula, so peridot is always green, from yellowish olive to vivid lime, never any other color. Major sources include Arizona's San Carlos Apache reservation, Myanmar, Pakistan's mountain deposits, and historically Zabargad Island in the Red Sea. Hardness 6.5 to 7 — fine for most jewelry with sensible care.
A magnesium aluminium oxide that crystallizes in crisp octahedra and spans red, hot pink, violet, cobalt blue and steel gray. For centuries its finest reds were mistaken for ruby — the 170-carat "Black Prince's Ruby" in the British Imperial State Crown is actually spinel — which is precisely why the trade associations added it as August's third stone in 2016: a historic, durable (Mohs 8), usually untreated gem that had never had a month of its own.
The ancient August stone: a banded chalcedony layering reddish-brown sard with white onyx bands. Because the flat, contrasting layers carve beautifully, sardonyx was the signet and cameo stone of the classical world — Roman soldiers wore sardonyx intaglios of Mars into battle. It is affordable, widely available, and the right choice when August calls for something with two thousand years of provenance rather than sparkle.
What color is the August birthstone?
The August birthstone color is green — specifically peridot's yellowish, olive-to-lime green, one of the most recognizable single-color signatures in gemstones. Charts, birthstone jewelry and "August color" lists almost universally use light green for the month.
The 2016 addition of spinel quietly gave August a second palette: fine spinels run red, pink, violet and cobalt blue. So a gift does not have to be green to be an August birthstone anymore — but if you are matching the conventional chart color, peridot green is the answer.
How August got its birthstones
Peridot's story starts on Zabargad (St. John's Island) in the Red Sea, where Egyptians mined "the gem of the sun" over 3,000 years ago; a persistent tradition holds that some of Cleopatra's famous "emeralds" were actually peridot, and medieval crusaders carried the confusion into European church treasuries. The 1912 US standardization gave August to sardonyx; peridot arrived as its modern partner in the 1952 revision and gradually became the month's default stone.
Spinel's 2016 addition — announced jointly by the American Gem Trade Association and Jewelers of America — was the list's first change since tanzanite in 2002, and something of an act of historical justice: chemistry in the late 1700s had revealed that many of the world's most celebrated "rubies," including crown jewels, were spinel all along, yet the stone spent two centuries in ruby's shadow.
Choosing & caring for August birthstones
Peridot: color drives value — richer, purer green beats yellowish olive — and eye-clean stones are the norm, so visible inclusions should lower the price. Its softness (6.5–7) and sensitivity to sudden heat and acids argue for pendants and earrings over hard-worn rings, and for keeping it away from ultrasonic cleaners. Spinel: usually untreated (a genuine rarity in colored stones) — reds and cobalt blues command the top prices, grays and violets are the value corner; lab-grown spinel exists widely in class rings, so ask. Sardonyx: inexpensive — pay for the quality of banding and carving, and check that strong red-white contrast is natural rather than dyed.
Frequently asked questions
What is the August birthstone?
August has three official birthstones: peridot (the familiar modern stone), spinel (added by the US trade associations in 2016) and sardonyx (the traditional stone, on lists since 1912 and in use for centuries before). Peridot is the conventional answer; all three are correct.
What color is the August birthstone?
Green — peridot's olive-to-lime green is the standard August color on every chart. Spinel's 2016 addition technically widened the month to reds, pinks and blues, but green remains the conventional answer.
Why was spinel added to August?
In 2016 the American Gem Trade Association and Jewelers of America named spinel August's third stone — the first list change since 2002. Spinel earned it on merit: a hard (Mohs 8), brilliant, usually untreated gem whose finest reds were historically mistaken for ruby, including the 'Black Prince's Ruby' in the British crown.
Is peridot ever any color other than green?
No — and that is unusual. Iron, the element that colors it, is part of peridot's chemical formula rather than an impurity, so the mineral is green by definition. What varies is the shade: more iron pushes it toward deeper olive, less toward yellow-lime.
How do I tell peridot from emerald or green glass?
Peridot's green always carries a yellow undertone; emerald's green is bluer and deeper. Under a loupe, peridot's strong double refraction visibly doubles the back facet edges — glass and emerald don't do that. Glass often contains round bubbles and feels warmer in hand. A photo through our identifier plus the peridot field guide covers the rest of the checks.
See the full birthstones-by-month chart or jump to December, June, October.
Last updated 2026-07-18