If you want the short answer, buy peridot. Sardonyx held the month first and spinel joined in 2016, so all three sit on the current list. Peridot is the one you will be offered.
In 2010 a geo-archaeological expedition landed on a small island off Egypt’s southern Red Sea coast and went looking for a mine that had existed, until then, mainly in Roman literature. They found the workings, the ruins of the buildings around them, and a well.
The island is Zabargad and what came out of it was peridot. GIA calls Zabargad the oldest recorded source of August’s birthstone and puts the start of mining there at around 340 to 279 BCE.
Getting from a name in a Roman book to a hole in that particular ground took two centuries and three separate pieces of work.
The island in the Roman record
Pliny the Elder places the source of the stone on a Red Sea island called Topazos. Reading him alongside the archaeology, James Harrell and Lisbet Thoresen take Pliny, quoting King Juba, as recording that the island mine was first opened under Ptolemy II Philadelphos, and that a gift of the stone was presented to Berenice, the king’s mother. The ruler is named, the recipient is named, and so is the island.
What went missing was the island. For most of the seventeen centuries after Pliny wrote, no Western scholar could say which piece of the Red Sea he meant, and Harrell dates the identification of Topazos with Zabargad to the beginning of the nineteenth century.
The stone was a separate question, settled a hundred years later again. Harrell puts the recognition of what the Zabargad gemstone is in the first decade of the twentieth century, first by Bauer in 1904. Geography first, then mineralogy, about the same rock.
Even that left the mine itself as a piece of literature. Zabargad’s geology has been studied for decades and its modern workings are on record, but the ancient mine was not, and Harrell writes that one “had not been verified until a geo-archaeological expedition to the island in 2010 confirmed the existence of ancient mine workings and associated ruins of buildings and a water well.”
Reading the pottery and the written sources together, Harrell puts the ancient mine’s working life at “nearly 800 years, an interval spanning most of the Hellenistic (323 to 30 BC) and Imperial Roman (30 BC to AD 476 in the West and later in the East) periods.” That is a long time to keep a site running on an island with those conditions, and GIA notes the island’s reputation in the names it collected: Island of Death, and Ophiodes, snake island.
Sardonyx, and the reason a Roman reached for it
Sardonyx has the older claim on the month. When the American trade printed a standard list in 1912, August’s line read sardonyx, with peridot beside it in the second column.
Sardonyx is banded chalcedony, which is quartz grown in crystals too small to see, so the stone reads as solid rather than crystalline. GIA describes it as a combination of two kinds of chalcedony, sard and onyx, with bands of brownish red to brown to dark orange sard alternating with white or black layers.
Those parallel bands are what a carver buys it for, and they support two opposite jobs. A cameo stands the image up in relief, cutting a pale layer back so a figure sits against the dark one beneath. An intaglio sinks the image into the surface instead, which is what makes it come back the right way round when it is pressed into something. GIA notes that the colour banding has kept sardonyx in use for both for millennia.
The reason Romans reached for it was practical before it was decorative. GIA puts it flatly: “In ancient times, sardonyx was a popular stone for Roman seals and signet rings, as hot wax would not stick to it.” A seal that releases cleanly is a seal that works, and the banding a carver wanted came attached to a stone that already did the job.
The Blacas Cameo in the British Museum is the great surviving demonstration of what the layers could do. The museum records it as a three-layered sardonyx carved with a portrait of Augustus wearing the aegis of Minerva and a sword belt, dated to AD 14 to 20. The modelling is done in the thickness of the layers. The one part of the head that is not carved is the jewelled setting Augustus now wears, which the museum’s record says replaced his original laurel wreath, probably in the medieval period.
Spinel’s late arrival
Spinel is the newest name on the twelve-month calendar. Jewelers of America and the American Gem Trade Association announced the addition together, and National Jeweler reported it on 2 June 2016.
The case the trade made was a case about a long misunderstanding. Doug Hucker of the AGTA gave the reasoning in that report: “Ancient gemstone merchants revered spinel, and it was widely sought after by royalty. It was then known as ‘balas ruby.’ It wasn’t until the late 18th century that we developed the technology acumen necessary to distinguish spinel as a separate mineral from ruby…”
The best-known result of that confusion is in the Imperial State Crown. GIA describes the roughly 170 carat Black Prince’s ruby passing through a succession of Moorish and Spanish kings before Edward, Prince of Wales received it in 1367, and dates the separation of spinel from ruby to the eighteenth century. The stone kept the name it had been given in the centuries when the two could not be told apart, and it keeps it today.
For a buyer the practical fact is hardness. GIA puts spinel at 8 on the Mohs scale and calls it typically durable for rings and other jewellery, which makes it the hardest of August’s three by a clear margin.
Peridot’s two addresses
Peridot is the gem form of olivine, and GIA describes it as formed under extreme conditions, found in hardened lava that carried it up from deep within the Earth’s mantle. The stone belongs to the layer underneath the crust, and it is at the surface because something carried it there.
Something else brings it too. GIA writes that peridot “has also come to Earth via pallasite (made of nickel-iron and olivine) meteorites,” while giving the proportions: thousands of meteorites have hit the Earth, many of them containing olivine, and only a few have held gem-quality peridot. The stone in an August ring is almost certainly terrestrial. The point is that it need not have been.
Most of what reaches a shop comes from somewhere far more recent than Zabargad in any case. GIA lists China, Myanmar, Pakistan, Tanzania, Vietnam and the United States among the working sources, and gives Arizona as the main American one, where lava that spread across what is now the San Carlos Apache Indian Reservation left peridot behind and Apache families have worked the mines for decades. There is a beach in Hawaii carrying enough olivine in its sand for GIA to describe it as shimmering a luminous green.
The care follows from the mineral. GIA puts peridot at 6.5 to 7 on the Mohs scale, softer than many gems, and advises against daily wear in a ring; acids damage it, and so does long exposure to acidic perspiration. Where peridot, sardonyx and spinel sit among the minerals, as opposed to among the months, is set out in the Crystalance Mineral Library, and the question of how any of the three came to be August’s in the first place is worked through in who chose your birthstone.
The 2010 expedition’s plainest find was the well. Somebody dug for water on an island with none at the surface, in heat that earned the place the name Island of Death, and then people kept the workings going there for the better part of eight centuries. Nobody did that for the view.
Sources
- GIA, August birthstones, on Zabargad and the mining dates, sardonyx, spinel, the Black Prince’s ruby, pallasite meteorites and hardness: gia.edu
- Harrell, James A., “Discovery of the Red Sea source of Topazos (ancient gem peridot) on Zabargad Island, Egypt,” pp. 16 to 30, and Thoresen, Lisbet, and James A. Harrell, “Archaeogemology of peridot,” pp. 31 to 51, both in Lisbet Thoresen (ed.), Peridot and Uncommon Green Gem Minerals: Twelfth Annual Sinkankas Symposium, Pala International, 2014: academia.edu
- The British Museum, the Blacas Cameo, museum number 1867,0507.484: britishmuseum.org
- National Jeweler, “JA, AGTA Add Spinel as August Birthstone,” 2 June 2016: nationaljeweler.com
