Fifteenth century magico-medicinal minerals

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Chris Duffin (UK)

The Hortus Sanitatis (1491)

On 23 June 1491, a new volume was printed and bound for distribution in the German University town of Mainz. The publisher was Jacob von Meydenbach, who might also have been responsible for compiling many of the entries in the book. The volume was based partly on an earlier work entitled Gart der Gesundheit, which was also published in Mainz, but this time by Peter Schöffer, an apprentice of Johannes Gutenberg.

This famous pioneer revolutionised mass product printing in the 1450s by developing the use of movable type. Schöffer continued to innovate in this medium after Gutenberg’s death in 1468, experimenting with page sizes, numbers of lines to a column, the arrangement of text blocks and font styles, and the use of woodcuts as illustrations. His Gart der Gesundheit, published in 1483, only a few decades after the inception of the printing revolution, was an immediate success. Meydenbach’s Hortus Sanitatis was prepared as a sort of sequel to the Gart; more ambitious in scope, it was rather longer with additional entries and, importantly for us, a section on stones (Fig. 1).

Fig. 1. A double page spread from the De Lapidibus section of Hortus Sanitatis (1491). Wellcome Collection, London.

Gart der Gesundheit (German) and Hortus Sanitatis (Latin) both translate as The Garden of Health, giving an indication of the thrust of the volume – here was a treatise on the medicinal virtues of materials from the natural world. The section on stones (De Lapidibus), like those in the preceding sections on plants, animals, birds and fishes, compiled information from a wide range of earlier sources, and included data concerning both real and mythical objects. Illustrated throughout by a set of woodcuts, some of which are delightfully bizarre, the work appeared in numerous later printings from a variety of publishing houses – there was no such thing as copyright law at the time, and some publishers specialised in producing ‘reprints’ of successful volumes. This is effectively the publishing of fifteenth century pirated editions. The last printing was in 1552.

De Lapidibus – the section on stones

The Hortus Sanitatis contains 1,066 chapters, with 144 entries in the section on stones. The frontispiece to De Lapidibus depicts a covered market with artisans and traders displaying their wares on wooden tables, while potential customers with appropriate means meander between the stalls singly or in groups (Fig. 2). Both geological hand specimens and worked materials, such as cabochons mounted in rings, are available for purchase, and the woodcut communicates a real sense of active business; the vendors demonstrate their stock and appeal to passers by to examine their specimens, and are prepared to engage in discussion with prospective customers with appeals to the authority of the books that accompany their displays. It has all the airs of a modern mineral show.

Fig. 2. Frontispiece of the De Lapidibus section of Hortus Sanitatis (1491), depicting a medieval mineral fair.

Fifteenth century medicine

Medical treatment in the fifteenth century was bound up in a completely different world view influenced by numerous philosophical systems, some of which are fairly alien to us today, at least in that context. The prevailing view of disease relied upon the humoral system championed by classical medical scholars, such as Hippocrates in the fourth century BC and Galen in the second century AD.

Disease was seen as being caused by an imbalance in the humours. Trained persons identified the humoral imbalance from the suite of symptoms showed by the patient, and treatment was designed to restore the correct balance. This invoked an Aristotelian idea – it was believed that the qualities residing in plants, animals and stones could be harnessed to balance opposing conditions in the body. For example, if a person ran a fever with much sweating, they would be demonstrating hot and wet qualities.

The appropriate treatment would therefore involve the administration of natural remedies whose intrinsic qualities were cold and dry. In addition to this, astrology was seen as an important factor in health; the stars and the heavens were seen to have a direct influence on all aspects of life on earth, once expressed in the famous dictum ‘As above, so below’. Furthermore, it was believed that God had provided remedies in the natural world for all the ailments suffered by mankind. Helpfully, he had left a series of signs by which these therapeutic materials could be identified. This was expressed in the ‘Doctrine of Signatures’. The interpretation of the humoral, astrological and divinely appointed influences on human health was the province of the specially trained elite.

Medicinal stones

The entries for the various stones in the Hortus Sanitatis are characteristically accompanied by a woodcut, which may illustrate a feature of the specimen, its means of collection or use. This is followed by a section, which often gives some idea of the different names by which the material might be known, how it might be identified, where it can be found, and any interesting or distinctive features that it might display. Finally, the therapeutic qualities of the rock, mineral, fossil or earth are highlighted, sometimes with brief details as to how it should be administered and what it can be mixed with, so as to achieve the optimum benefits. This information is tied throughout to carefully selected references to earlier authoritative writings. These include, for example, the Historia Naturalis of Pliny the Elder, Greek and Roman physicians and philosophers, such as Aristotle, Hippocrates and Galen, medieval Arabic writers such as Avicenna, and medieval western authors such as Marbode of Rennes and Isidore of Seville.

When it comes to identifying the stones being described or the diseases they were used to treat, things are not always very clear. Names which have a quite restricted modern definition might embrace a wide range of possibilities in older literature. Topazos, for example, might be expected to refer to the aluminium silicate gemstone topaz, but in ancient times, it was more commonly applied to peridot, the gem variety of the mineral olivine. Similarly, the disease scabies might mean the dermal rash caused by mites, but often encompassed a wide range of other skin conditions. Clearly, the mineral and medical terminology both need some careful interpretation. Fortunately, as far as the geological materials are concerned, descriptions and figured specimens in later sixteenth and seventeenth century works by such authors as Conrad Gessner and Olaus Worm provide further clues from which more confident identifications can be made.

Limitations of space make it impossible to provide a complete survey of all the ‘stones’ covered in the Hortus Sanitatis. The selection that follows has been chosen either because of the interesting therapeutic and magical properties or ‘vertues’, which the specimens were believed to possess, or for the delightful nature of the accompanying woodcuts (or both).

Gems and semi-precious stones

Fig. 3. Adamantus (diamond) from Hortus Sanitatis (1491; cap. i).

Adamantus is the Latin name for diamond and the word from which we get the term ‘adamantine’, referring both to a type of lustre and the hardness of a particular mineral. During the fifteenth century, virtually all diamonds available on the market came from India. The image accompanying the description of this gemstone (Fig. 3) is, at first glance, rather incongruous – it shows a man seated at a table on which there sits an oval bowl and a sort of brazier. This image relates to the information in the text, which explains that fire cannot break diamond down and that the only thing that can soften or break the mineral is goat’s blood, especially from an animal that is fed on good wine, mountain sedge or parsley.

The man is therefore simultaneously assaying specimens to prove that they are the genuine article and breaking the ones he has confidently identified into smaller pieces. The extreme hardness of the mineral could supposedly be transferred to the owner, so that he would become strong while resisting his enemies. It could also repel vanity, venom and lunacy. Diamond was also recommended as a component in dentifrices (tooth-cleaning powders) – it would certainly be effective at removing plaque and tartar, but probably also the enamel covering the tooth. This must have been a very expensive toothpaste.

Fig. 4. Ametistus from Hortus Sanitatis (1491; Cap. vii).

The wine colour of amethyst (Ametistus), a popular crystal for mounting as cabochons in rings, was supposedly indicative of the mineral’s ability to protect the bearer from becoming drunk (Fig. 4).

Fig. 5. Corneolus from Hortus Sanitatis (1491; cap. xliii).

Carnelian (Corneolus), a reddish-orange variety of chalcedony, was esteemed because of its colour. Like many red minerals it was believed, by the Doctrine of Signatures, to have virtues that related to the blood. In this case, it was believed to be very effective at reducing blood loss, especially during menstruation and in cases of haemorrhoids. It is difficult to discern the significance of the accompanying illustration (Fig. 5).

Fig. 6. Cristallus from Hortus Sanitatis (1491;
cap. xxxix).

Cristallus or rock crystal (quartz) was held under the tongue to quench the thirst and taken as a powder in honey to ensure that the milk continued to flow without difficulty in nursing mothers and wet nurses (Fig. 6). It was accorded styptic qualities – the ability to stem bleeding.

Fig. 7. Gagates (Jet) from Hortus Sanitatis (1491; cap. lviii).

Following Pliny’s statement that the best Gagates or jet comes from Britain, the Hortus Sanitatis states that it is good for resisting demons and enchantments. The fumes from burning jet were believed to drive away vermin, especially snakes. Specimens heated and held under the nose were supposed to be able to diagnose epilepsy; and powdered jet drunk in a draught of water or wine was used to treat toothache and intestinal problems (Fig. 7).

Fig. 8. Granatus (garnet) from Hortus Sanitatis (1491; cap. lx).

Granatus is the garnet, much revered as a precious red gemstone. The image shows the means by which true and false examples were discriminated from each other (Fig. 8). The semi-naked test subject, grasping or wearing a garnet ring, was smeared with honey and forced to lie on the floor (the supervisor is clearly taking no chances that he will make a bolt for it, by standing on the subject’s feet). Wasps and flies were then released; if they landed on the prone gentleman, it proved that the stone was a fake – true examples of the stone possessed the power to force the insects away. Garnets were believed to strengthen the heart. If carried in the mouth, it conferred upon the bearer the ability to accurately weigh the opinions and ideas of others. Women would wear this stone to make them pleasing to their menfolk.

Fig. 9. Iacinctus (zircon) from Hortus Sanitatis (1491; cap. lxv).

Iacinctus refers to jacinth or hyacinth, red zircon, which was credited with the power to comfort and strengthen the body, make a person agreeable to their host (if worn about the neck or on the finger), promote restful sleep and protect against the poisons that one might meet in ‘pestiferous’ countries (Fig. 9).

Fig. 10. Iaspis (jasper) from Hortus Sanitatis (1491; cap. lxvi).

It was recommended to carry or wear Iaspis or jasper for protection against fevers and dropsy (oedema). It also supposedly had the power to combat fascination by witchcraft, to help pregnant women and to regulate menstruation and other cases of bleeding (Fig. 10).

Fig. 11. Sapphirus (sapphire) from Hortus Sanitatis (1491; cap. cix).

Rubeus or ruby was hailed as a particularly pleasing stone. When contemplated and held up to the light, it was able to banish all signs of melancholy, to strengthen the individual and to heal any eye problems that might be present. The sapphire (Sapphirus) was likewise highly esteemed and thought to help keep a person chaste, as well as easing pains in the forehead and tongue (Fig. 11). It was also said to increase a person’s devotion to God, peace and wellbeing, as well as expelling ‘the fires of fever’. The sapphire was also claimed to eliminate the disease known at the time as Noli me tangere (‘Touch-me-not’). This is generally believed to be what medieval physicians called the ‘hidden cancer’ (cancer absconditus); patients could not bear to have tumorous swellings investigated by touch.

Fig. 12. Succinum (amber) from Hortus Sanitatis (1491; cap. cxxii).

Amber (Succinum) is quite accurately described in terms of its colour and the contexts in which it is found. The accompanying image (Fig. 12) shows it as a resin exuded from an injury on the trunk of a tree. This origin had been suggested much earlier than the fifteenth century, but many contemporary works still relied on the legendary origins associated with Phaeton, or the suggestion that it represented the congealed rays of the setting sun trapped in the ocean, as it disappeared over the horizon. As with jet, burning of the material was thought to produce vapours and smoke which drove away serpents. Possession of a piece of amber was believed to help promote chastity and to maintain the health of children.

Fig. 13. Topazion (peridot) from Hortus Sanitatis (1491; cap. cxxxii).

The image accompanying the text of Topazion (Fig. 13) illustrates the belief that the mineral was able to cool boiling water; it depicts a man placing a piece of the mineral into a pot of water on a fire, which is dangerously close both to himself and the table on which his specimens sit. Rather than representing topaz, this mineral actually refers to peridot. Like many other stones, it was believed to staunch excessive blood loss, as well as suppressing anger and lust.

Ores and metals

Fig. 14. Emathites (haematite) from Hortus Sanitatis (1491; cap. li).

Emathites refers to the iron oxide mineral, Haematite. Often identified by its cherry red streak, the red colour of this mineral indicates its therapeutic use. It was deemed particularly useful in cases of nosebleed, as the accompanying image shows (Fig. 14), but almost any example of bleeding could be treated. It was also commended for the ‘bloody flux’ – probably amoebic dysentery – and mixed with wine to treat ulcers and bladder stones, which it would supposedly disperse.

Fig. 15. Magnes (magnetite) from Hortus Sanitatis (1491; cap. lxxvii).

Magnes clearly refers to magnetite or the loadstone. This is especially obvious from the text, which describes the magnetic properties of the mineral, and the accompanying illustration (Fig. 15), which depicts a ship sailing too close to a mountain made of the material with the unfortunate consequence that all the iron nails have been drawn out of the timbers causing the ship to sink and the crew to be thrown into the sea. This seemingly magical power of the mineral helped to justify its therapeutic use in stopping ‘flux of the belly’ (diarrhoea), dropsy (oedema) and eliminating poisons from the body. It is also credited with the eminently useful property of being able to identify an adulteress. If placed underneath the head of a sleeping woman, the magnetite will cause a faithful and chaste wife to turn over directly into her husband’s arms. If she is an adulteress, however, she will end up falling out of bed.

Fig. 16. Cerussa (hydrocerussite) from Hortus Sanitatis (1491; cap. xxxv).

Cerussa is the Latin name for white lead, a hydrated lead carbonate occurring mineralogically as hydrocerussite, a weathering product of various lead ores. Even in the late fifteenth century, it was used to whiten the face, but the Hortus Sanitatis also indicates that it was used to treat tooth decay and halitosis. Formed into plasters, its drying properties were exploited in the treatment of ulcers and deep-seated abscesses or apostumes. It is not entirely clear why the accompanying image depicts a woman seemingly in the act of consuming frogs (Fig. 16).

Other minerals

Fig. 17. Arsenicum (arsenic) from Hortus Sanitatis (1491; cap. xxii).

Two varieties of Arsenicum (arsenic) are recognised (Fig. 17) – a yellow and a red form (orpiment and realgar respectively). Applied to the scalp, it was recommended for alopecia, and as an oil or ointment to the skin it was used to treat dermal complaints. In addition, it was believed to stop blood flow, ease haemorrhoids and be effective against ‘old coughs’ and spitting of blood (haemoptisis).

Fig. 18. Melochites (malachite) from Hortus Sanitatis (1491; cap. lxxxii).

Melochites is described as being a splendid green mineral and the associated woodcut presents a tolerable rendition of the reniform occurrence of the hydrated copper carbonate, malachite (Fig. 18). Worn as an amulet, it was believed to preserve people from accidents and to protect young children from danger.

Fig. 19. Selenites (selenite gypsum?) from Hortus Sanitatis (1491; cap. lxxxii).

The name Selenites still lives on in the fibrous form of gypsum. As the word intimates, it is a mineral associated with the Moon (‘Selenos’ is Greek for moon). If that were not clear, the accompanying image reinforces the concept – a man stands at a table covered in tablets of the mineral, all with smiling faces – representations of the ‘Man in the Moon’ (Fig. 19). Carried on the person, it was believed to guard against languor, breathing problems (phthisis) and general debilitation.

Fig. 20. Tartarus (Tartaric Acid) from Hortus Sanitatis (1491; cap. cxxix).

Tartarus is the mineral-like hard residue that builds up on the insides of wine vats and barrels. Essentially made up of Cream of Tartar or Tartaric Acid, it is also known as algol. Clearly, it is included in the Lapidibus section of the Hortus Sanitatis because of its mineral-like appearance. It is included here as an excuse to share the delightful accompanying figure (Fig. 20), with the labourer fully immersed in the barrel, successfully hacking out the tartarus rind, complete with builders’ cleavage. The material was used to treat impetigo and to cleanse the body from impurities.

Rocks and earths

Fig. 21. Arena (sand) from Hortus Sanitatis (1491; cap. xii).

Several lithologies are depicted in the Hortus Sanitatis, and the accompanying images (Figs. 21 to 26) mostly show men in the process of extracting the material (for example, Arena or sand (Fig. 21) and Argilla or clay (Fig. 22) – Latin terms from which we also get the names for the arenaceous and argillaceous classes of clastic sedimentary rocks).

Fig. 22. Argilla (clay) from Hortus Sanitatis (1491; cap. xiii).

A mixture of clay in strong vinegar was pressed to the temple to halt nosebleeds.

Fig. 23. Bolus Armenus (Armenian bole) from Hortus Sanitatis (1491; cap. xxvi).

Armenian bole (Bolus Armenus) was a red earth whose colour indicated its efficacy as a haemostatic – it was commended for stopping bleeding (Fig. 23). As a drying medicine, it was also believed to be useful against catarrhs, lung problems (phthisis, which probably included tuberculosis), cataracts and ulcers.

Fig. 24. Lazuli (Lapis lazuli) from Hortus Sanitatis (1491; cap. lxxi).

Lazuli is the name by which Lapis lazuli was known (Fig. 24). The sole contemporary source of this rock was the remote mountains of Badakshan in Afghanistan. The delightful, heavenly blue colour of the lazurite component of this metamorphic rock accounts for the belief that it was able to disperse melancholic humors and thereby lift the spirits of the debilitated owner. It was also believed to cleanse the blood of ‘gross humors’ and to promote menstruation in cases of late periods or amenorrhoea (cessation of menstruation). It could also be used as a laxative and to cause vomiting, both of which were seen as useful treatments to void the body of any humors, which were in harmful excess. It was also said to cheer and strengthen the heart.

Fig. 25. Pumex (pumice) from Hortus Sanitatis (1491; cap. cv).

Pumex refers to the extrusive volcanic igneous rock, pumice (Fig. 25). The entry for this rock in the Hortus Sanitatis shows a man seated before a fire, carefully adjusting a pile of heated stones, emphasising the volcanic origins of the material. Reduced to a powder, it was recommended as an abrasive for incorporation into dentifrices with which to clean the teeth, and also as a means of cicatrising (helping scar formation) wounds and ulcers, including those sustained by the eyes.

Fig. 26. Terra sigillata (‘sealed earth’) from Hortus Sanitatis (1491; cap. cxxx).

Terra sigillata were samples of (usually) marly clay, mined with great pomp and ceremony, pressed and fashioned into discs or troches and authenticated with specially impressed seals, as shown in the specimens being displayed on the table in front of the gentleman in the picture (Fig. 26). Highly acclaimed as alexipharmic medicines (neutralising and expelling poisons), they were administered in a variety of ways – ground and mixed with vinegar, for example, or mixed with honey to form a clyster (enema). In addition to acting as an antivenin, powdered terra sigillata was esteemed in the treatment of ulcers, apostumes (abscesses) and stomach upsets, and to strengthen the heart.

Stones from the bodies of living creatures

This group includes a number of stones whose roots lay in folklore and legend. Whilst the details of the origins (and uses) of these materials may not always be factual, most of them are represented in other literature and museum collections by actual geological materials. The concept of stones being engendered in the bodies of living organisms could easily have been defended by quoting kidney stones, bladder stones and other heterotopic bones and concretions, which would have been well known at the time.

Fig. 27. Alectorius (Capon stone) from Hortus Sanitatis (1491; cap. vi).

Alectorius or the Capon Stone was said to be found in the belly of a castrated rooster; the accompanying image shows the undignified process of extraction (the bird on the ground clearly has no idea as to what fate awaits him). Held in the mouth, it was credited with being able to assuage thirst and ensure that a man is invincible. Worn by a woman, it supposedly made her graceful, beautiful and completely irresistible (Fig. 27). In the possession of a man, it conferred many admirable personal qualities on him – eloquent speech, constancy and being highly personable. It was also believed to increase his libido. Alectorius was probably the grit swallowed by poultry (gastroliths) as an aid to digestion.

Fig. 28. Bezaar (Bezoar stone) from Hortus Sanitatis (1491; cap. xxiiii).

Bezoar stones are accumulations of undigested matter found in the digestive tracts of many animals, especially ruminants. Calcium and phosphate salts may precipitate around the undigested material and bind it together; growth of the stone takes place in a centrifugal manner. It was believed to be a particularly effective antivenin, whether the poison was introduced into the body from a serpent or insect bite, or through an infection such as the plague. It could be taken as a powder, scraped from the stone surface and suspended in a draught of water, or worn mounted in a ring, drawing the poison out through the skin. The venom or poison was eliminated from the body through copious sweating. The man in the image (Fig. 28) accompanying the text entry for this stone is clearly in need of some sort of rapid intervention.

Fig. 29. Chelidonius (Swallow stone) from Hortus Sanitatis (1491; cap. xxxiii).

Chelidonius is also known as the Swallow Stone. Like Alectorius, it was supposedly extracted from the living bird (Fig. 29). Two sorts were identified – a red one and a black one. Wrapped in a yellow cloth and tied around the left arm, the red variety was able to cure lunacy and epilepsy, as well as conferring the qualities of friendliness, loquacity and grace. Ground to dust and used to irrigate the eye, it was believed to cure various ocular problems.

Fig. 30. Cinaedia (fish otoliths) from Hortus Sanitatis (1491; cap. xxxiiii).

Cinaedia is a stone that is reported to be found in the brains of certain fish – the name refers to the otoliths, which are used as gravisensory organs (Fig. 30). The accompany image shows a man scouring the beach and a rather disgruntled fish, with an enormous cranial swelling (indicating the presence of the otolith), waiting to have its precious stone harvested for the good of mankind. This magical stone was said to be able to predict the coming of storms and to make the sea tranquil.

Fig. 31. Draconites (Dragon stone) from Hortus Sanitatis (1491; cap. xlvii).

The image accompanying the entry for Draconites (Fig. 31), the Dragon Stone, shows a man cutting open the belly of the beast to retrieve the stone. Once harvested, this mythical stone was believed to act as a sovereign antivenin and to make a man invincible in battle.

Fig. 32. Borax (Toad stone) from Hortus Sanitatis (1491; cap. xxvii).

The Toad Stone appears in the Hortus Sanitatis under several names, one of which is Borax. The accompanying image shows a man extracting the stone from the head of a large, old toad (Fig. 32). Another stone which was revered as an indicator and protector against poison, whether administered from outside the body or the result of a disease, it was recommended to swallow this stone to cleanse the bowels of any poisonous impurities.

Since the Toad Stone can be identified from later works as the crushing teeth of Mesozoic semionotiform fish, such as Lepidotes and Scheenstia, the swallowing of such a specimen must have been no mean feat – the teeth are commonly 10mm or more in diameter. There was the added benefit, however, that the specimen could be re-used once it had been retrieved from its passage down the gut. It could even be treated as a family heirloom, with successive generations able to benefit from its therapeutic virtues.


It may come as a surprise that geological materials and those that qualitatively resembled them in some way, should have been credited with such a wide range of therapeutic and prophylactic properties. Clearly, having an extensive geological collection in medieval times could have benefits that went far beyond the acquisitive and aesthetic.


The information concerning the supposed therapeutic benefits of geological materials discussed here is a matter of intellectual and historical interest only. On no account should any of these materials be used medicinally – indeed, many of the items listed here are toxic.


I am grateful to the Countway Medical Library for permission to use images from their copy of the Hortus Sanitatis; and the Wellcome Library, London for permission to use one of their images from the Wellcome Collection.

About the author

Chris Duffin is a Scientific Associate in the Earth Science Department at the Natural History Museum in London; and a Research Associate in the Earth Science Department at Bristol University.


1491. Hortus Sanitatis. Mainz: Jacob Meydenbach.

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