Stones for astrology: the history behind zodiac gemstones

The breastplate, and the leap that followed

Exodus 28 describes a breastplate worn by the Hebrew high priest set with twelve stones in four rows, one for each of the twelve tribes. This is the oldest text anyone points to when they claim gemstone associations are ancient, and the claim is half right: the twelve stones are ancient, and the astrology isn't in the text.

The link was made later. Josephus, writing in the first century CE, observed in Antiquities of the Jews that the twelve stones could be understood as corresponding to the twelve months and the twelve signs of the zodiac. St Jerome repeated the comparison around 400 CE. That interpretive leap (from twelve tribes to twelve signs, on the strength of both being twelve) is the foundation of everything that came after.

There is a further complication that gemstone sellers rarely mention: nobody is certain which stones the Hebrew names refer to. The identifications shift between the Hebrew, the Greek Septuagint and the Latin Vulgate, and modern translations disagree with each other. A list presented as unbroken from Exodus is a list that has been reconstructed several times.

The lapidary tradition

For most of the medieval period, stones weren't connected to birth dates at all. They were connected to virtues: powers a stone was held to possess regardless of who wore it.

The dominant text in Latin Europe was the Liber lapidum of Marbode, Bishop of Rennes, written around 1090. It described sixty stones and what each was good for, drawing on earlier Greek and Latin sources, and it was copied and translated across Europe for centuries. Its concerns are medical and protective: this stone stops bleeding, that one wards off poison.

The Indian tradition ran in parallel and is older in written form. The Ratnapariksha attributed to Buddha Bhatta, from around the sixth century CE, is a technical text on the examination and valuation of gems. The nine-gem navaratna setting, with each stone assigned to one of the nine grahas of Vedic astrology, belongs to this lineage and is the one tradition on this page that still makes an active prescriptive claim.

By the Renaissance the astrological connection was explicit. Camillo Leonardi's Speculum Lapidum of 1502 covered engraved gems and the astrological images cut into them, which is closer to talismanic magic than to jewellery.

The 1912 jewellers' list is the one everyone uses, and I think it should embarrass anyone who calls birthstones ancient.

When did people start wearing their own birth month?

Later than you would expect, and the evidence is thinner than the confidence with which it's repeated.

The usual account holds that the practice of owning all twelve stones and wearing each in its month gave way to owning only the stone of your own birth month, and that this shift happened in eighteenth-century Poland or Germany among gem traders. That account is repeated everywhere and rests on very little primary evidence. Treat it as a plausible story, not a documented fact.

What is documented is that by the nineteenth century the idea was current in English-speaking countries, helped along by verse, the month-by-month birthstone poems that circulated in Victorian gift books did more to fix the associations in ordinary minds than any lapidary ever did.

1912, and who wrote the history

In 1912 the National Association of Jewelers, meeting in the United States, adopted a standardised list of one stone per month. It was a commercial act with a commercial purpose: a customer who knows their birthstone knows what to buy, and a jeweller who knows the customer's birth month knows what to stock.

The list has been revised repeatedly since, and the revisions are the clearest evidence of what it is. Alexandrite, citrine and pink tourmaline were added in the 1950s. Tanzanite (a stone discovered in Tanzania in 1967 and unknown to any tradition before then) was added to December in 2002. Spinel joined August in 2016. No ancient system acquires new members by committee.

And there's a detail to sit with. The standard, most-cited history of gemstone lore in English is The Curious Lore of Precious Stones, published in 1913 by George Frederick Kunz. It is a learned book and most popular birthstone histories are downstream of it. Kunz was also the chief gemologist of Tiffany & Co. The definitive account of why these stones matter was written, one year after the trade standardised the list, by a man whose employer sold them.

The three lists, side by side

If two sites give you different birthstones, neither is wrong. They're answering different questions from different traditions, and only one of those traditions has ever had an official list.

The 1912 list, month by month, and what has changed

Every addition gave a month a second, more affordable or more available stone, which is what a trade list is for. The 2002 addition was announced by the American Gem Trade Association, and tanzanite is mined in one place on Earth, in northern Tanzania, by companies that were pleased with the decision.

The navaratna, stone by stone

The one tradition on this page that still prescribes is the Indian nine-gem system, and its logic is planetary, not calendrical. Each of the nine grahas has a stone, and a Vedic astrologer prescribes one to strengthen a planet the chart is held to need.

Two things follow from the substitute column. The first is that the tradition itself allows cheaper stones, which counts when a prescription insists on the expensive one. The second is that the prescription is the astrologer's judgement about which planet needs help, and two astrologers can name different planets from the same chart, so the stone you are told to buy depends on who you asked.

What 'natural and untreated' means for the price

Remedial prescriptions usually specify a natural, untreated stone of a minimum weight, often several carats. That specification is why the bill is large. Most sapphire on the market has been heated to improve colour, which is accepted in the trade and disclosed; an unheated blue sapphire of good colour costs several times as much. Rubies are commonly glass-filled, emeralds oil-treated. A gemological laboratory report from a body such as GIA or SSEF states what was done, and a stone sold as untreated without one is a stone you are taking on faith.

The prescription and the supply chain are the point to hold together. A practitioner who both names the planet and sells the stone is paid for finding a problem. Ask for the report, ask why the substitute would not do, and remember that no trial has found a gemstone doing anything a placebo did not.

What is known about what stones do

Nothing therapeutic. There's no demonstrated effect of wearing or carrying a gemstone on health, mood, luck or personality, and where trials have been run the results match placebo.

Nobody should delay medical treatment for a stone, and the prescriptive traditions are the ones where money changes hands. A Vedic remedial stone must typically be natural, untreated and of a specified weight, which puts a prescription into the hundreds or thousands, and the prescription frequently comes from someone in a position to supply it.

AsterNym computes a stone set from your chart and presents it as correspondence, not remedy. We tell you where each association comes from, and we don't sell stones. That last part is the relevant disclosure.