Biogenic Gem Materials & CITES
To clarify and remove any possible ambiguity from a trade term that is used to name or classify products in the jewellery industry, CIBJO, came up with a new expression during a Pearl Commission meeting held in its 2016 Congress in Yerevan, Armenia. This new expression that would collectively refer to any gem material derived from living organisms was agreed to be "biogenic", that basically relates to a biological origin.
The expression organic was maintained but it would be used for biogenic gem materials that are essentially composed by organic matter or organic molecules, as defined in chemistry. Under the new terminology, organic gem materials now include, for example, tortoiseshell, horn, black coral, copal and the so-called vegetable "ivory", and, by its own definition, rule out the gem materials that are essentially composed by biomineralised substances, like calcium carbonate in the form of aragonite or calcite, including pearls, cultured pearls, mother-of-pearl, shells and precious corals.
For the sake of clarity, although fossils, like amber, ammolite, opalised molluscs, silicified wood and mammoth ivory, as well as other materials of biological origin found in a geological context like jet (not technically a fossil) may have had in their origin a living organism, these are not considered biogenic gem materials strictum sensum.
Instead of elaborating on a selection of gem materials of biological origin, of which cultured pearls are probably the most relevant ones in the jewellery trade today, it was decided that a conservation perspective was in order under the spirit of United Nations Decade on Biodiversity. This means that, along with other gem materials, the vast majority natural and cultured pearls will not be covered here as well as the historically relevant precious coral species of the Mediterranean since the species that produce them are not listed in the Convention on International Trade of Endangered Species (CITES), as per the last Conference of Parties held in Geneva in 2019 (www.cites.org).
CITES APPENDIX I
CITES APPENDIX II
CITES APPENDIX III
CITES LISTED SPECIES
APPENDIX I
Rhinoplax vigil (Forster, 1781)
This large tropical bird of the Bucerotidae family that lives in Asia namely in Indonesia, Thailand, Malaysia and Myanmar, known as the helmeted hornbill, develops, especially in the males, a large beak that has a yellow to red keratinous thick covering known in the trade as hornbill ivory. It has been known as a gem material at least since the Ming dynasty in China. The trade name of this gem material includes the word "ivory" which is considered a misnomer since it is not a tooth from a mammal but rather a keratinous covering over a bone structure. Nevertheless, as one may verify in many particular situations in our trade, tradition has crystallized this trade term, being therefore generally accepted as it is.
Photo © Skullsite
Rhinocerontidae spp.
The few existing species of rhinos of the Rhinocero- ntidae family in Africa and Asia, including the white rhinoceros, Ceratotherium simum (Burchell, 1817), the Sumatran rhinoceros, Dicerorhinus sumatrensis (G. Fischer, 1814), the black rhinoceros, Diceros bicornis, (Linnaeus, 1758), the Javan rhinoceros, Rhinoceros sondaicus (Desmarest, 1822) and the great Indian rhinoceros, Rhinoceros unicornis (Linnaeus, 1758), develop a rather typical protuberance above their nose, sometimes a rather long one up to 150 cm long, that is commonly known as a horn, more specifically rhino horn. Again, this trade name carries another technical terminology inaccuracy since this material is not exactly horn, as we may see in bovids, but rather an agglomerate of long hardened hairs without a bone internal structure. Again, tradition has made this trade term generally accepted.
Photo: Libation cup, Jiangsu, China. Rhino horn mounted on silver filigree (Manila?) 17th century, second half. Private Collection, OnShot/Rui Carvalho. Museu do Oriente
Physeter macrocephalus (Linnaeus, 1758)
The large cachalot, also known as sperm whale, is the largest existing toothed whale with males easily reaching 15 meters long, living in almost all oceans and latitudes. The 32 to 52 teeth on the lower jaw can grow up to 25 cm long and have been used as sperm whale ivory in tools and decorative arts for centuries as a by-product of the whale hunting for their meat and oils. New England sailors while on board whale ships in the 19th century used to kill time by carving these whale teeth and also whale bones, a technique that would eventually become known as scrimshaw.
Photo, scrimshaw © Peter Cafe Museum
Loxodonta spp. & Elephas spp.
African elephants, Loxodonta Africana (Blumenbach, 1797) and Loxodonta cyclotis (Matschie, 1900) and Asian elephants, Elephas maximus (Linnaeus 1758) that develop a sometimes very long pair of teeth, especially the males, are among the most controversial sources of ivory, having been at the centre of rather intense discussions in several countries on their trade even as antiques. The fact is that the species are listed in Appendix I, with some exceptions in certain geographies, and therefore deserve mentioned here.
Elephant ivory has been the most used type of ivory in the decorative arts, marquetry or musical instrument manufacture, due to its size, texture and carving adequacy. Distinguishing elephant ivory from other types of ivory from other living mammals (e.g. hippo, cachalot, warthog, orca, walrus) can be tricky if one does not have enough visual experience. More difficult is separating ivory from living elephants from the extinct mammoths, notably the woolly mammoth Mammothus primogenius (Blumenbach, 1799). Al- though a careful observation of the engine turned growth structures seen perpendicular to the growth direction, known as Schreger lines, might give fairly good indications in most cases, DNA fingerprinting and, more recently, carbon-14 dating has been suggested as a test to separate century-old ivory of elephants from a fossil material from other species, typically older than 10,000 years.
In the last CITES CoP in 2019, a suggestion was made to include the woolly mammoth in CITES Appendix II. Although the species needs no protection since it has been extinct for thousands of years, the purpose was to fight illegal trade in living elephants by preventing "laundering" or mislabelling of elephant ivory. The proposal was, however, not approved.
Photo: SIngalo-Portuguese, 16th century, Sri Lanka © PAB
Eretmochelys imbricata (Linnaeus, 1766)
The hawksbill sea turtle has been the most common source of scutes for the decorative arts that are known in the trade as tortoiseshell, another misnomer since the animal is not technically a tortoise but a turtle. Other marine species like the green turtle, Chelonia midas (Linnaeus, 1758) or the log- gerhead turtle, Caretta caretta (Linnaeus, 1758), have also been used but to a much lesser extent since their individual scutes are not as good quality as the hawksbill’s.
Tortoiseshell, a natural plastic (a polymer, just like rubber or shellac that are also technically natural plastics), is typ- ically light yellow with dark brown areas when it is from the dorsal carapace of the turtle. The ventral protection scutes are, on the other hand, of an homogeneous yellow colour and are much thinner that the dorsal counterparts, being known in the trade as "blond tortoiseshell". Individual dorsal scutes are usually rather thin (up to 12 mm, however thicker than other turtles’ scutes) and somewhat large (averaging 20 cm in maximum length) and it was the outstanding thermo- plastic properties of this attractive material that enabled craftsman to work them in intricate shapes and sizable artefacts of marquetry and other decorative objects.
Photo: 16th centuryCasquet, tortoiseshell and silver mountings. Gujarat, India. Mid-16th century © Diocese de Beja
Appendix II
This large thick-skinned semiaquatic African mammal has very long and characteristic front teeth, namely the incisives and the canines, that have a non-enamelled area suitable to be used as hippo ivory, being denser and with a finer texture than African elephant ivory.
Photo Rebecca Hale © National Geographic
Monodon monoceros (Linnaeus, 1758)
This mid-sized whale species from the cold Artic waters, commonly known as narwhal or sea unicorn, develop in males a long spiral incisive tooth, up to 3 meters long, that is essentially hollow through its length. Its shape has long been associated with the legendary unicorn, an imaginary creature romanced for thousands of years in history, hence its trade name "unicorn horn", being more accurately described, however, as narwhal ivory.
Lobatus gigas (Linnaeus, 1758)
Formerly known as Strombus gigas in the biological literature, the queen conch, a large edible gastropod that lives in shallow waters in the Caribbean up to Florida, has been primarily captured for the food industry, namely to make traditional local dishes like the conch salad. The shell, especially the part where pink is more evident, is often used as a by-product namely for the manufacture of drilled beads. The most important by-product is, however, the lovely and very rare non-nacreous conch pearl that in their best examples have an oval shape, pink colour and, most specially, a well visible flame structure caused by the cross lamellar microstructure of the calcium carbonate crystals. Conch pearls have been also seen in the trade as "Pink pearls" or "Nassau pearls".
Being listed on Appendix II of CITES since 1992 have inspired the scientific community to try culturing techniques. In 2009, the Florida Atlantic University’s Harbour Branch Oceanographic Institute did just that and an operation was reportedly set up in Honduras produc- ing 3 to 8 mm cultured conch pearls at an experimental, non-commercial, level.
Photo: Marjorie Merriweather Post's Cartier pendant brooch ca. 1922 © Hillwood Estate, Museum & Gardens
Tridacna spp.
The so-called giant clams of the Tridacneridae family, especially the Tridacna gigas (Linnaeus, 1758), T. maxima (Röding, 1798) or T. squamosa (Lamarck, 1819) species, have been long captured for their beautiful, large shells, often weighing much more than 100 kg, that are still seen in catholic churches as Holly Water vessels. These large bivalves have also produced very occasional non-nacreous white pearls with a very characteristic flame structure, known as clam pearls, that may reach considerable sizes, reportedly from 3 mm to 140 mm. In some cases, very large natural blisters have also been reported on these clams, notably the 6.37 kg Pearl of Allah and the 2.27 kg Palawan Princess Pearl, both from the Philippines.
Tridacna shell has been also used as an imitation of other pearls, namely melo pearls after a dying process that turns the shell into an orange colour. It is believed that the so-called "coconut pearls", alleged rare concretions found inside coconuts in Asian tropical areas, have been manufac- tured from Tridacna shells, in this case Tridacna maxima. As a note, it appears that Tridacna species shell was briefly used as a shell bead, usually over 8 mm, in pearl farms.
Photo © Smithsonian Institution
Antipatharia spp.
The corals of the order Antipatharia that occur basically worldwide are typically very dark brown to black and have non-calcareous skeletons, being mostly composed of protein and chitin, which gives them a much lower specific gravity and heft than other common or precious corals composed of calcium carbonate. These so-called black corals have been bleached to obtain a golden coloration (golden coral). CIBJO does not classify these corals as precious coral, since it does not belong to the Corallidae family. This nomenclature standard is specific of the gem and jewellery trade under CIBJO since in the biological literature, the term "precious coral" applies to all corals suitable for decoration, including the now mentioned antipatharians.
Photo © Doug Menadue/Bespoke Gems
Heliopora coerulea (Pallas, 1766)
This is the only reef building coral that is currently still considered as a material of fairly reasonable gemmolog- ical interest. Defined as a common coral, and not as a precious coral in the jewellery trade nomenclature, it has a calcareous composition, a distinct blue colour and a porous skeleton, typically requiring resin impregnation to be used as ornament. Blue corals, also known in the trade as blue ridge coral, blue sponge coral or denim coral, occur in Indo-Pacific shallow waters in coral reefs.
Photo © Maggie Campbell Pedersen
Sylaster spp.
The so-called lace corals of the Stylaster genus are common corals of a pink to violet to red colour, having aragonitic composition that distinguishes them from the precious coral species of the Corallidae family that have calcitic composition. To the less observant, Stylaster corals may be somewhat similar to the precious corals of the Corallidae family after being fashioned, dyed and impregnated. Their presence in jewellery artefacts is, however, very limited.
Photo © Marine Themes Stock Photo Library
Diospyros spp.
Ebony is a collective name for the dark and dense exotic wood produced by species of the Diospirus genus and also from the Mozambican Dalbergia melanoxylon (Guillermin & Perrottet), locally known as "pau preto" (black wood). The Diospyrus species from Madagascar and the abovementioned Mozambican ebony are listed on Appendix II. Apart from their use in marquetry, notably in Indo-Portuguese 16th and 17th century furniture, and musical instrument manufacture, ebony has been seen also in jewellery, namely in rings and bracelets, usually set with gemstones.
Photo, bracelet made in 1985 in gold, chalcedony, diamonds and a 75.41 ct high-quality amethyst, by JAR © Christie's
APPENDIX III
Odobenus rosmarus (Linnaeus, 1758)
This large marine mammal of cold Artic waters, commonly known as walrus, has two long upper canine teeth that have been traditionally used as walrus ivory for tools and decoration by the local fishing communities, namely in Canada, Alaska, Greenland and Scandinavia, and is closely related to indigenous northern circumpolar peoples’ culture where it was primarily used to manufacture hunting tools and more recently for decoration.
Photo © Metropolitan Museum of Art
Pleurocorallium elatius (Ridley, 1882)
This is a precious coral species, formerly known as Corallium elatius, that lives at depths of 150 to 350 meters in Japan and Taiwan, being the largest of all precious coral species. Biologists have included it in the Pleurocorallium elatius species-complex that gathers three species of the Pleurocorallium genus (P. elatius, P. konojoi and P. Wcarusrubrum). This precious coral is typically red to salmon or orange-coloured, with a white interior often call "soul", a variety known in the trade as momo,satsuma or cerasuolo coral. On rare occasions, rare albino individuals are reported, occurring in a characteristic light pink colour known in the trade as angel’s skin or as boké in Japanese. Intermediate light pink colours are usually termed magai. This precious coral variety has been used in the orient for the manufacture of artistic carvings since the 19th century, the reported period of its discovery.
Photo, angel's skin earrings by Bulgari ca. 1970 © Sotheby's
Corallium japonicum (Kishinouyi, 1903)
This is the most valuable precious coral species with significant popularity in the Orient. it is dark red to very dark red, with a typical lengthwise white interior that enables its separation from the non-listed Corallium rubrum from the Mediterranean. This species lives in Japan at depths of 80 to 300 meters, being known in the trade as aka, moro or oxblood coral, this last one in English.
Photo © Chii Li Coral
Pleurocorallium konojoi (Kishinouyi, 1903)
The so-called pure white coral, also known in the trade as shiro (white in Japanese), is a uniform milky-white precious coral that has been pointed as member of the Pleurocorallium elatius species-complex, that lives in depths of 80 to 300 meters in the South China Sea close to Hainan in Vietnam.
Photo © Kawamura Coral
Corallium secundum (Dana, 1846)
This is the obsolete taxon of Pleurocorallium secundum, a precious coral species of uniform white to pink colour, sometimes with small red specks, known in the trade as Rosato, Midway coral. It lives in depths of 400 to 600 meters in Hawaii and Midway Island, in the Pacific Ocean, and was discovered in the 1960s, with no fishing reported since 2001. Light pink varieties are often erroneously classified as angel’s skin.
Photo, Midway coral bracelet © Liverino 1894
Adapted and edited from Galopim de Carvalho, R. (2020). “Biogenic Gem Materials”, Gamma, The ICA | GemLab Journal, 1(3), 22-29
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