The Canterbury Tales’ Prioress, more concerned with luxury than fighting luxuria, notoriously carries a set of prayer beads ending not in a cross but in a pendant inscribed with “Love conquers all.” Chaucer’s mention of its dainty coral beads is no idle description—polished coral, like gems and minerals, held significant meanings and powers in the medieval imagination.
In the late fourteenth and fifteenth centuries, in fact, coral was undergoing a change in meaning. To high medieval scholars like Thomas of Cantimpré, the branching nature of living coral took the shape of Christ’s cross, giving it strong powers as a ward against things like storms and epilepsy. By the early modern era, coral amulets promised success in earthly, lustful love. Chaucer’s use of coral, therefore, seems to add to the devotional ambivalence of the character.
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Most of us today are probably familiar with the concept of birthstones—precious gems associated with each month, like a petrological Zodiac. It turns out birthstones are more or less an invention of modern jewelry manufacturers, whose meanings all boil down to “Buy this ring.” But this is boring. So I thought, why not make birthstones mean something today by looking at their superpowers according to the Middle Ages?
Fortunately, there’s an entire genre of texts known as lapidaries, from authors like Bartholomeus Anglicus and Albert the Great, to help us out!
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The Magical Stones of March: Summoning Demons and Boiling Clouds
Aquamarine stone with the portrait of Julia Domna (died AD 217), the wife of Emperor Septimius Severus.
Aquamarine is a form of beryl, to which were attributed all sorts of fantastical powers.
…except medieval lapidary authors’ descriptions make it clear their idea of beryl was really clear rock quartz. So instead, the stone “diacodos” or substitute was lightly colored quartz or beryl, like aquamarine. It was a favorite of magicians in the Hermetic tradition—perhaps used for some crystal-gazing fortune telling, but also supposed to help a person summon demons.
What gives, March? Your other birthstone, bloodstone, also had a much stronger presence in necromantic texts than quasi-scientific ones (and not because of its vaguely creepy modern name—it was called “heliotropium” in the Middle Ages and linked to the sun). According to ancient magicians repeated by medieval authors, a bloodstone placed in water could darken the sun, turn its light blood-red, and boil the clouds into thunderstorms.
It was also said to stop bleeding, but who needs that when you can trigger a solar eclipse on demand?
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April’s Diamond: Madness, Nightmares, and Drunk Goats
Medieval gold and diamond ring – The Portable Antiquities Scheme/ The Trustees of the British Museum
Tired of having an expensive but ubiquitous birthstone? Grab a time machine! Thanks to the tremendous hardness of diamond and skill needed to cut it properly, medieval lapidaries (the people, not the books) didn’t really bother to invest the time to master the optics of refraction to make diamond look like it does today. So writers like Thomas of Cantimpré were first of all concerned with describing ways to destroy it. For example, soaking the stone in the blood of a goat—especially a drunk goat—might soften it enough to make it cuttable.
Diamonds could, however, protect the wearer against insanity and nightmares. Now that is how to market an engagement ring.
Emeralds in May: Riches, Prophecies, and Broken Rings
Emerald ring – British Musuem
The green beryl we know as emerald was, in the Middle Ages, one of the recognized types of a gemstone category/variety called “smaragdus” (or the more recognizable esmaraldus). Consequently, an enormous set of abilities granted to individual varieties came to apply to the whole group. Wearing an emerald amulet could help you win arguments, get rich, cure epilepsy, prevent thunderstorms, improve your memory, and predict the future.
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Well, as long as you don’t have sex. Albert the Great repeats a legend that the King of Hungary wore an emerald ring to bed. The stone was so upset even by lawful intercourse between the king and queen, that it shattered into three pieces.
June’s Moonstone: Secrets of the Lunar Cycle
7th century broach with moonstones – photo courtesy Metropolitan Museum of Art
Perhaps unsurprisingly, many qualities attributed to moonstone in the Middle Ages related to the moon. It was said to grow and shrink with the moon’s waxing and waning, with its powers peaking on certain lunar days. The moonstone was above all a tool for divination: placing it under your tongue could inculcate knowledge of a specific action one must take (or not).
…As for pearl, really the most important thing we learn is that Albert the Great really liked eating oysters and often ended up with a mouthful of pearls for his haste in consuming them.
The Fiery Ruby of July: Poison and the Glow of Mars
14th century gold ring with a ruby – The Metropolitan Museum of Art
The ruby was another gem invested with poison-neutering ability, but most of its reputation related to its deep clear red color—the color of Mars. Its monetary value to jewelers depended on how much it shone in the dark: not at all, only when water was poured over it, or all on its own “like a live coal.”
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Also, congratulations—your birthstone in Greek is “anthrax.”
August Gems: Sardonyx and Peridot in Battle and Beyond
Byzantine cameo made of sardonyx from the 14th-century, – image courtesy Walters Art Museum
Sixteenth-century heraldry and arms encyclopedist Gerard Legh carefully acknowledged his debt to the medieval lapidary tradition when he noted that sardonyx could “put away lechery” and keep its bearer chaste in thought and action. But he added a military meaning onto the usual set of mystical attributes of stones. Sardonyx reminds its bearer that in battle, care is better than haste.
As a form of olivine, peridot was typically tagged as chrysolitus in medieval lapidaries. Thus, it was considered one of the twelve stones building the walls of the New Jerusalem in Revelation 21. This was of far less concern to lapidary authors—even the theologians in religious orders!—than its medical, magical, and moral powers. Marbode of Rennes said to wear peridot in a gold setting as a bracelet on your left wrist, from which it could ward off nightmares and demons. Albert the Great said he knew from observation and testing that if you ground peridot to a powder, it could cure asthma. And “expel stupidity.” Clearly, a fitting birthstone for a common “back to school” month!
Sapphire in September: A Gem of Wealth and Wisdom
Byzantine pendant showing the Virgin and Child – includes pearls, emeralds, garnets, sapphires, and a sardonyx – Metropolitan Museum of Art
What we know today as sapphire was most probably identified as the blue form of hyacinthus or iacinthus in medieval sources. A blue “having nothing watery about it” hue was considered the most valuable form.
October’s Opal: Vision, Mystery, and Invisibility
Opal “Lunar Disc” outside Salisbury Cathedral – Peter Barr / Wikimedia Commons / CC BY-SA 2.0
Ancient and medieval authorities worried that staring too long at opal, trying to capture all its colors, would damage people’s eyesight. Either for that or for the similarity of its Latin name (ophthalmus) to ophthalmia the eye disease, it was associated with vision but in a deeply ambivalent way. It could protect the eyes of its wearer as an amulet, but harm others.
Oh, yeah, and it could turn you invisible.
Topaz in November: Fool’s Gold and Fiery Cures
Late Roman Topaz ring stone – photo courtesy Metropolitan Museum of Art
In the Middle Ages, topaz was thought to take the forms either of the clear orangey-yellow stone we know today or a mockery of gold—our pyrite or fool’s gold. As the transparent topaz, it could instantaneously cool boiling water or cure hemorrhoids; as pyrite, it could scare off tornadoes.
The Colors of December: Turquoise for Luck, Lapis Lazuli for Art
Medieval bead made from Lapis Lazuli – photo courtesy Metropolitan Museum of Art
Albert the Great describes the color and opaqueness of turquoise: “as if milk had penetrated the blue color and risen to the surface.” Turquoise was said to heal eye problems, and amulets were worn to ward off basically every kind of misfortune.
Lapis lazuli was considered effective against disorders caused by excessive black bile, particularly fever and fainting. (Sometimes it was considered a form of sapphire with the attendant powers…the more valuable form!) However, lapis lazuli is the semi-precious gem whose primary special use was artistic rather than medical. It was the source of the famous (and infamously expensive) pigment ultramarine so loved by late medieval and Renaissance painters—at least, those who could afford it.
Garnet in January: The Happy Gem of Gladness
7th-century gold necklace pendant inlaid with a garnet. Photo Birmingham Museums Trust / Wikimedia Commons
The stones medieval people recognized as garnet tended to be darker red or red-violet than rubies. Jewelers recommended setting them against black. Garnet was the happy gem! Forget poison prevention—garnet warded off sorrow and brought gladness.
Amethyst in February: The Sobering Stone
Medieval gold pin head in the form of a fleur de lys with amethyst inlay – The Portable Antiquities Scheme/ The Trustees of the British Museum
Amethyst was said to prevent drunkenness.
Somehow this never shows up in sermons against gluttony.
By Cait Stevenson
The Canterbury Tales’ Prioress, more concerned with luxury than fighting luxuria, notoriously carries a set of prayer beads ending not in a cross but in a pendant inscribed with “Love conquers all.” Chaucer’s mention of its dainty coral beads is no idle description—polished coral, like gems and minerals, held significant meanings and powers in the medieval imagination.
In the late fourteenth and fifteenth centuries, in fact, coral was undergoing a change in meaning. To high medieval scholars like Thomas of Cantimpré, the branching nature of living coral took the shape of Christ’s cross, giving it strong powers as a ward against things like storms and epilepsy. By the early modern era, coral amulets promised success in earthly, lustful love. Chaucer’s use of coral, therefore, seems to add to the devotional ambivalence of the character.
Most of us today are probably familiar with the concept of birthstones—precious gems associated with each month, like a petrological Zodiac. It turns out birthstones are more or less an invention of modern jewelry manufacturers, whose meanings all boil down to “Buy this ring.” But this is boring. So I thought, why not make birthstones mean something today by looking at their superpowers according to the Middle Ages?
Fortunately, there’s an entire genre of texts known as lapidaries, from authors like Bartholomeus Anglicus and Albert the Great, to help us out!
The Magical Stones of March: Summoning Demons and Boiling Clouds
Aquamarine is a form of beryl, to which were attributed all sorts of fantastical powers.
…except medieval lapidary authors’ descriptions make it clear their idea of beryl was really clear rock quartz. So instead, the stone “diacodos” or substitute was lightly colored quartz or beryl, like aquamarine. It was a favorite of magicians in the Hermetic tradition—perhaps used for some crystal-gazing fortune telling, but also supposed to help a person summon demons.
What gives, March? Your other birthstone, bloodstone, also had a much stronger presence in necromantic texts than quasi-scientific ones (and not because of its vaguely creepy modern name—it was called “heliotropium” in the Middle Ages and linked to the sun). According to ancient magicians repeated by medieval authors, a bloodstone placed in water could darken the sun, turn its light blood-red, and boil the clouds into thunderstorms.
It was also said to stop bleeding, but who needs that when you can trigger a solar eclipse on demand?
April’s Diamond: Madness, Nightmares, and Drunk Goats
Tired of having an expensive but ubiquitous birthstone? Grab a time machine! Thanks to the tremendous hardness of diamond and skill needed to cut it properly, medieval lapidaries (the people, not the books) didn’t really bother to invest the time to master the optics of refraction to make diamond look like it does today. So writers like Thomas of Cantimpré were first of all concerned with describing ways to destroy it. For example, soaking the stone in the blood of a goat—especially a drunk goat—might soften it enough to make it cuttable.
Diamonds could, however, protect the wearer against insanity and nightmares. Now that is how to market an engagement ring.
Emeralds in May: Riches, Prophecies, and Broken Rings
The green beryl we know as emerald was, in the Middle Ages, one of the recognized types of a gemstone category/variety called “smaragdus” (or the more recognizable esmaraldus). Consequently, an enormous set of abilities granted to individual varieties came to apply to the whole group. Wearing an emerald amulet could help you win arguments, get rich, cure epilepsy, prevent thunderstorms, improve your memory, and predict the future.
Well, as long as you don’t have sex. Albert the Great repeats a legend that the King of Hungary wore an emerald ring to bed. The stone was so upset even by lawful intercourse between the king and queen, that it shattered into three pieces.
June’s Moonstone: Secrets of the Lunar Cycle
Perhaps unsurprisingly, many qualities attributed to moonstone in the Middle Ages related to the moon. It was said to grow and shrink with the moon’s waxing and waning, with its powers peaking on certain lunar days. The moonstone was above all a tool for divination: placing it under your tongue could inculcate knowledge of a specific action one must take (or not).
…As for pearl, really the most important thing we learn is that Albert the Great really liked eating oysters and often ended up with a mouthful of pearls for his haste in consuming them.
The Fiery Ruby of July: Poison and the Glow of Mars
The ruby was another gem invested with poison-neutering ability, but most of its reputation related to its deep clear red color—the color of Mars. Its monetary value to jewelers depended on how much it shone in the dark: not at all, only when water was poured over it, or all on its own “like a live coal.”
Also, congratulations—your birthstone in Greek is “anthrax.”
August Gems: Sardonyx and Peridot in Battle and Beyond
Sixteenth-century heraldry and arms encyclopedist Gerard Legh carefully acknowledged his debt to the medieval lapidary tradition when he noted that sardonyx could “put away lechery” and keep its bearer chaste in thought and action. But he added a military meaning onto the usual set of mystical attributes of stones. Sardonyx reminds its bearer that in battle, care is better than haste.
As a form of olivine, peridot was typically tagged as chrysolitus in medieval lapidaries. Thus, it was considered one of the twelve stones building the walls of the New Jerusalem in Revelation 21. This was of far less concern to lapidary authors—even the theologians in religious orders!—than its medical, magical, and moral powers. Marbode of Rennes said to wear peridot in a gold setting as a bracelet on your left wrist, from which it could ward off nightmares and demons. Albert the Great said he knew from observation and testing that if you ground peridot to a powder, it could cure asthma. And “expel stupidity.” Clearly, a fitting birthstone for a common “back to school” month!
Sapphire in September: A Gem of Wealth and Wisdom
What we know today as sapphire was most probably identified as the blue form of hyacinthus or iacinthus in medieval sources. A blue “having nothing watery about it” hue was considered the most valuable form.
October’s Opal: Vision, Mystery, and Invisibility
Ancient and medieval authorities worried that staring too long at opal, trying to capture all its colors, would damage people’s eyesight. Either for that or for the similarity of its Latin name (ophthalmus) to ophthalmia the eye disease, it was associated with vision but in a deeply ambivalent way. It could protect the eyes of its wearer as an amulet, but harm others.
Oh, yeah, and it could turn you invisible.
Topaz in November: Fool’s Gold and Fiery Cures
In the Middle Ages, topaz was thought to take the forms either of the clear orangey-yellow stone we know today or a mockery of gold—our pyrite or fool’s gold. As the transparent topaz, it could instantaneously cool boiling water or cure hemorrhoids; as pyrite, it could scare off tornadoes.
The Colors of December: Turquoise for Luck, Lapis Lazuli for Art
Albert the Great describes the color and opaqueness of turquoise: “as if milk had penetrated the blue color and risen to the surface.” Turquoise was said to heal eye problems, and amulets were worn to ward off basically every kind of misfortune.
Lapis lazuli was considered effective against disorders caused by excessive black bile, particularly fever and fainting. (Sometimes it was considered a form of sapphire with the attendant powers…the more valuable form!) However, lapis lazuli is the semi-precious gem whose primary special use was artistic rather than medical. It was the source of the famous (and infamously expensive) pigment ultramarine so loved by late medieval and Renaissance painters—at least, those who could afford it.
Garnet in January: The Happy Gem of Gladness
The stones medieval people recognized as garnet tended to be darker red or red-violet than rubies. Jewelers recommended setting them against black. Garnet was the happy gem! Forget poison prevention—garnet warded off sorrow and brought gladness.
Amethyst in February: The Sobering Stone
Amethyst was said to prevent drunkenness.
Somehow this never shows up in sermons against gluttony.
Cait Stevenson earned her PhD in medieval history from the University of Notre Dame. She is the author of How to Slay a Dragon: A Fantasy Hero’s Guide to the Real Middle Ages. You can follow her on BlueSky @anyfourcastles.bsky.social
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