Biogenic Gem Materials in Artefacts of Portuguese Heritage in the 16th-17th Centuries

Biogenic Gem Materials in Artefacts of Portuguese Heritage in the 16th-17th Centuries

The Portuguese discoveries that opened the sea route to India by Vasco da Gama in 1498 initiated what we now call early modern Globalisation. This India Run ("Carreira da India" in Portuguese) generated a greater availability of exotic materials for the decorative arts, including jewellery. Diamonds, pearls, sapphires, rubies, spinels (sometomes called “ballas”) and hessonite garnet, all from various far away regions, can be seen in greater numbers after the commencement of this maritime oriental trade route. Another impact of no lesser importance, was the involvement of oriental artisans in the manufacture of commissioned precious objects, generally included is what is called “Exotica”, using local materials and local techniques to create decorative or functional objects serving an European, sometimes, devotional narrative. These objects manufactured, for example, in regions today known as Sri Lanka, India, China, Japan and the Philippines, were presented and traded in Lisbon to Portuguese and European merchants that anxiously awaited the arrival of the oriental ship convoy of the India Run to source exotic goods for their wealthy customers. Lisbon became then the first global city with people, animals, plants, materials and objects from all over the known world. Among these goods, there was a significant variety of biogenic materials (also known in the gem literature as organic gem materials), including pearls, mother-of-pearl, ivory, tortoiseshell, bone, horn, bezoar stone, coco-de-mer and Mediterranean coral. Let’s have a quick look on some of these materials.

Unknown Netherlandish author 1570-1619. A view of the Rua nova dos Mercadores in Lisboa in the 16th century, where most exotica, gemstone and jewellery trade took place. London, Kalmscott Manor Collection, The Society of Antiquaries of London © by kind permission.


Tortoiseshell is the general name given to the plaques of the dorsal and ventral carapaces of certain marine turtles, specially the hawksbill turtle, Eretmochelys imbricata, and, more rarely, the green turtle, Chelonia mydas. The corneous translucent material from the dorsal carapace has a distinctive yellowish-brown colour with brown specs, and the up to 70 cm long carapace includes 13 plaques that can be as large as 20 cm. Its thermoplastic properties allowed it to be worked in a particular fashion that was suitable for embellishing decorative objects and jewellery.

One of the uses of tortoiseshell in Portuguese taste artefacts were decorative caskets and small chests that used either their dorsal plaques or ventral plaques with silver mounts. The ventral plaques are thinner with a light yellow color, being known in the trade as blond tortoise shell. In the illustrated example, a wood inner structure is covered with dorsal plaques of Eretmochelys imbricata with silver mounts, in a typical case of the so called indo-portuguese artistry manufactured in Gujarat, India.

Ivory is the material sourced from the teeth of large mammals, e.g. hippopotamus, walrus, orca, narwhal, warthog, sperm whale, but specially elephants, both African and Asian (in the later case only males). The oriental manufacture of ivory artefacts for an European clientele of the time has been extensively reported. However, some extremely rare 16th-century African manufactured objects are worth mention as the illustrated example, consisting of the central section of a salt-cellar made in Benin in equatorial Africa, carved from a tusk of an African elephant (Lexodonta spp.). In this very interesting piece we can see an armed Portuguese and a local man wearing a Mahican-style hair-cut, from who’s phallus vegetal branches emerge as symbols of fertility.
Photo © Paulo Alexandrino, private coll.
The nacreous interior of certain mollusks, especially the ones that exhibit iridescent effects (namely several pearl oyster species, Pinctada spp., some gastropods, like the great green turban,Turbo marmoratus, and abalone, Haliotis spp,) have been extensively used as decorations and in jewellery. Abalone mother-of-pearl is common in 16th-17th century Japanese objects made under Portuguese commission in a style known as Namban. In India, pearl oyster and green turban material were used in luxury objects like the chess and backgammon board here illustrated where the pink to green strong iridescent Turbo marmoratus plaques contrast with the more greyish tone of the pearl oyster species’ plaques.
Chess and backgammon board made in tortoiseshell and mother-of-pearl (Turbo marmoratus and Pinctada spp.) © Paulo Alexandrino
Bezoar Stone and Goa Stone
Certain ruminants, like goats, can form calcareous concretions in their digestive or urinary systems that are generates by the accumulation of fur, fibres and other substances depending on the animals’ diet. These concretions, known in Arabic as bãnzar (antidote), were thought to have special powers, namely to inhibit the action of poisons. In fact, these stones can be efficient as antidote of arsenic based poisons due to their composition rich in brushite and in a protein derived from the degradation of the animal’s fur. The Portuguese sourced these bezoars in Ormuz, in the Arabian Gulf, and commissioned special gold containers and gold filigree mountings to hold them in a sumptuous manner. A by-product of these stones, the Goa Stone, was manufactured using fragments of the bezoar mixed with other substances, having an almost metallic lustre and usually encased in specially made precious metal containers.
"Pedra de Goa" (Goa Stone) © Museu da Farmácia, Emanuel Santos Almeida
Many other biogenic materiais, some from exotic places, like narwhal incisive teeth (believed to be from the mythical unicorn), bone, natural pearls from Pinctada spp., rhinoceros horn and sea coconuts (Lodoicea maldivica), some of European origins, like the red Mediterranean coral (Corallium rubrum) were worked by Asian and African artisans using European models, mixing western narratives, sometimes with devotional significance, with local aesthetics and techniques. Many European collectors sourced these treasuries for their “Exotica” cabinets and these can be seen today in museums and private collections all over the world. The modern conservation issues that created CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora) in Washington D.C. in 1973, now regulate the trade in many of the biogenic gem materials presented in this review and special attention should be given to it in protection of biodiversity.
Acknowledgements: The author wishes to thank Maggie Campbell Pedersen and Hugo Miguel Crespo for their contribution and assistence.
Adapted from Galopim de Carvalho, Rui (2017) "Biogenic Gem Materials in Artefacts of Portuguese Heritage in the 16th-17th Centuries", Gems & Jewellery, 26, 3, pp. 42-43
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