Precious Corals an Overview

Precious Corals an Overview

Sustainability concerns pushed by climate change have put the issue of coral on the agenda of major trade organizations,  trade magazines and gemological conference organizers. The work of the Coral Commission created by CIBJO, The World Jewellery Confederation, in 2014, under the leadership of Vincenzo Liverino, revealed that there was a significant lack of basic knowledge on the corals that are used in jewellery, known in the trade as precious corals. This rather long article, originally published on the periodical of the ICA - International Colored Gemstone Association, is a contribution to a much needed coral education.

Corals in History

The use of coral as an adornment dates back to pre-history, as do many biogenic gem materials, with the Mediterranean being the only significant historical source for precious coral. The ancient use of red coral in remote areas away from the harvesting areas is yet another demonstration of the very old trade routes that linked the West with the East. As far back as the 1500s, maybe even before, the African kingdom of Benin in equatorial Africa, started to value red coral, even with monetary value, after trading with Portuguese navigators. Even today, Benin royalty still wears coral-strung vests for formal ceremonies. Tibet is another example of a region where coral was, and still is, very much appreciated and this relation with the Orient is not new. The Roman naturalist Pliny the Elder (23-79 AD) wrote about Mediterranean coral being traded to Asia.

The cultural and spiritual dimension of corals is rather old, most probably attending to its red colour that is traditionally connected with life as the colour of blood. Corals are mentioned in sacred documents, namely in translations of the Tanakh and the Bible (Job 28:18) and in the Holy Quran in Ar-Rahmân Sura (55:22-58). Its most relevant mention in the literature is in classical mythology, notably in the epic masterpiece "Metamorphoses" by Roman writer Ovid (Publius Ovidius Naso) (43 BCE-17 CE). In its 4th volume, Ovid recouints that Perseus, the epic protagonist, decapitates Medusa, a fierce but beautiful gorgon monster—whose gaze turned her enemies to stone—in order to set princess Andromeda free. Perseus then buried Medusa's head in the sand, covering it with leaves and branches, then taken into the sea by nymphs, and transformed into coral. This was the origin of the belief that coral possessed powers against poison, evil eye and epilepsy. This pagan tradition was reborn in the Middle Ages and the Renaissance, when coral was again considered a symbol of longevity and was used in devotional objects such as the unusual 14th century reliquary in the Machado de Castro National Museum in Portugal. Iconographic representations of children—Baby Jesus in particular—were commonly made wearing coral or associated with coral. A famous example is the Madonna della Vittoria by Andrea Montegna (1496) that resides in the Louvre Museum in Paris.

In the 18th century, the Kingdom of Naples established the Reale Compagnia del Corallo in Torre del Greco, following a long tradition of coral manufacturing. About that time, coral was recognized as being an animal and not a plant, a theory that had already been put forth by the famous Persian scholar Abu Al-Biruni (973-1048). Only after Jean-André Peyssonnel’s research in 1726 was the animal nature of corals finally accepted. The discovery of coral in Asia and the Pacific in the 1800s further contributed to the development of the industry in Torre del Greco and then expanded to Asia, most notably in Asia and Taiwan.
Precious Coral vs Common Coral
In the gem and jewellery industry, the terminology that is used to designate the corals that are suitable for jewellery made in precious metals is different from the terminology used in biology. Biologists use the term "precious coral" for all the species that may be used as decoration, whereas CIBJO on the other hand has defined "precious coral" with more strict boundaries, distinguishing them from "common corals".
The word coral it self applies to thousands of marine species of the phylum Cnidaria, particularly those from the Antozoa class, including the subclasses Octocorallia and Hexacorallia. Of these, only a few are suitable for use in jewellery and decorative arts, hence the term "precious coral", a name that the trading community uses to distinguish them from the numerous species of common corals that are not traditionally used in jewellery. According to the CIBJO Coral Book, precious corals, notably red, pink and white varieties with porcelain-like luster after polishing, are limited to species belonging to the family Corallidae, particularly the Corallium, Pleurocorallium and Hemicorallium genera. Common corals are defined as calcareous type, usually found in coral reefs (e.g. sponge coral, bamboo coral and blue coral) or non-calcareous type (non-mineralized corals), with a soft organic skeleton, such as black and golden corals (e.g. Anthipathes spp., Kulamanamana haumeaae). One major difference between precious and common corals , specially reef corals, is the depth at which they grow andthrive. Reef corals on coral reefs live in shallow waters, whereas precious corals live at greater depths and are harvested below 50 meters, some living down to 2000 meter deep. It is important to understand and clarify that corals used in the jewellery industry (precious corals) are not the same as the corals that live on coral reefs and which are threatened by climate change and ocean acidification. 
In the photo: before and after (March and May 2016), bleached and then dead reef coral, Lizzard Island, Great Barrier Reef © XL Caitlin Seaview Survey
Coral as a Gem Material
From the more than 7,300 species of corals, only a handful are used in jewellery and defined as precious corals by CIBJO in the industry's nomenclature standards. Precious corals range from white to orange or from white to red tones. Although each variety can be traced to the specific taxon (biological group) that generated it, the coral traders commonly refer to corals by their commercial names, which vary by geographical region and the local vernacular. These designations and trade names are transmitted through the supply chain and are what the consumer if familiar with at the retail level, although the use of just "coral" without any variety descriptor still is the most common designation, will all the misinterpretations that it may create (as coral is the collective name for thousands of species, so many of them endangered).
Identifying a gem material as a precious coral and not common coral (usually dyed) or an imitation product is not difficult for an experienced gemologist or coral trader. The task of properly identifying its original species, however, is better left to the specialist on a well equipped laboratory for trade element analysis and DNA sequencing, if possible. Sometimes, the same species produces material with different trade names due to different colors and distribution. Consumers and jewellers are increasingly requesting specific information about precious corals, particularly their species, mainly due to the perceptions of value that different types of coral have in the market.
In the photo: Corallium japonicum (oxblood or aka coral) branch © Chii Lih Coral
Relevant Precious Coral Varieties
Aka, Moro or Oxblood: Dark red to very dark red corals; lengthwise white interior; sometimes called soul; from Corallium japonicum; lives in Japanese waters at 80 to 300 m; fan- shape coral with an average height of 20 cm, trunk diameter of 12 mm, weight of 200 g. Dark red saturated oxblood coloured beads or cabochons are among the most sought after precious coral varieties worldwide, especially in large sizes that are rare. Aka means red in Japanese.
Momo, Cerasuolo, Satsuma: Bright red, salmon, orange and flesh; lengthwise white interior, from Pleurocorallium elatius (sometimes referred to as Corallium elatius); lives in Japanese and Taiwanese waters at 150 to 350 m; fan-shape coral with average height of 35 cm, trunk diameter of 35 mm, weight of 500 g; branches may reach over one meter in size, as this variety is the largest type of precious coral. Artistic coral carvings, namely of Asian manufacture, are usually made from this precious coral. Momo means peach in the Japanese language.
Angel Skin, Boké, Magai: Delicate flesh pink with different intensities; from a rare variety of Pleurocorallium elatius (sometimes referred to as Corallium elatius); lives in waters of Japan and Taiwan at 150 to 300 m; fan-shape coral with average height of 35 cm, trunk diameter of 25 mm, weight of 500 g. The lovely pink of this almost albino precious coral has many aficionados in the high-end jewellery segment and is probably the most popular coral variety after the traditional Mediterranean red coral.
Pure White or Shiro: Milky white, sometimes with red or pink specks; from Pleurocorallium konojoi(sometimes referred to as Corallium konojoi); lives in waters of Vietnam and Hainan at 80 to 300 m; fan-shape coral with average height of 35 cm, trunk diameter of 25 mm, weight of 500 g. This coral is somewhat similar in shape to Momo and Boké, but the color is overall white, hence the name shiro in Japanese.
Midway, Rosato or White/Pink: Veined white or pink, sometimes with red specks or uniform clear pink; from Pleurocorallium secundum (sometimes referred to as Corallium secundum); in waters of Hawaii and Midway Island at 400 to 600m; fan- shape coral with average height of 25 cm, trunk diameter of 15 mm, weight of 200 g.
Deep Sea or Shinkai: Bright white, clear pink or white pomegranate with red veins or spots; from Hemicorallium laauense (sometimes referred to as Corallium secundum); in waters of Midway, northwest of Emperor Seamont, at 1000 to 2000 m; fan-shape coral with average height of 30 cm, trunk diameter of 10 mm, weight of 150g. The most striking characteristic of these corals is the color distribution, where a uniform white to pink background is decorated with reddish veins, cracks or spots.
"Garnet" coral: Pomegranate color with different shades of uni- form pink; from Hemicorallium regale(sometimes referred to as Corallium secundum); lives in Hawaiian waters at 350 to 600 m; parallel-shape coral with average height of 15 cm, trunk diameter of 6 mm, weight of 100 g; usually small in size. It is distinguished by its characteristic color, hence the name garnet. Harvest ceased in the 1980s due to the high costs of the operation.
Misu, Missu or Miss: Pink to violet uniform color; from Hemicorallium sulcatum (sometimes referred to as  Corallium secundum); lives at 100 to 300 m in waters north of the Philippines, Taiwan, Japan (Boso Peninsula); long-shape coral with average height of 25 cm, trunk diameter of 15mm, weight of 200 g.
Sardinian or Mediterranean: Uniform red with medi- um to strong saturation; from Corallium rubrum; lives in the Mediterranean and Atlantic areas of northern Africa at 60 to 1000m; bush-shape coral with average height of 15 cm, trunk diameter of 8 mm; weight of 100 g. Most historical artefacts are embellished with Mediterranean coral, since it is the most popular variety and is responsible for the association of precious color with the color red.
Sciacca: Orange, pink and dark smoky orange color; from Corallium rubrum; found in geological sediments at various depths in the south of Sicily of the coast of Sciacca; often broken branches or trunks with average height of 7-10 cm, trunk diameter of 4 mm; were collected as sediments, not as a product of fishing, since the 1870s and the deposits are currently depleted; similar deposits have been reported in the Alboran Sea, south of Spain, in Malta and elsewhere in Sardinia. The the huge output from famous Sciacca deposit, averaging 30m in stratification thickness, is estimated in excess of 14,000 tonnes, which caused great impact in the coral industry and decorative arts.
In the photo: Contamporary art by Jan Fabre using Mediterranean Coral selected by Enzo Liverino © Jan Fabre ; Below, Sciacca coral being trimmed at Liverino 1894 factory in Torre del Greco © Rui Galopim de Carvalho
Coral Treatments and Imitations
There are various processes to change the appearance and/or durability of precious coral. These include fissure filling, heating, dying and impregnation with artificial polymers and coating. Surface waxing with a colourless agent, on the other hand, is not usually considered a treatment, but rather a normal lapidary procedure as it is understood by industry standards and, therefore, corals that were processed and polished using a colourless wax, namely parafine, must not be classified as treated coral.
A number or natural and artificial products have been used to imitate coral, including paste, plastics, porcelain, vegetable "ivory" (also known as tagua, corozo or jarina), dyed bone, barium sulphate with plastic, chalcedony and dyed marble. In the 1970s, Pierre Gilson introduced an artificial product composed of calcite powder and pigmentation referred to in the trade as synthetic coral or Gilson coral.
All of these coral imitations are easily detected using visual observation and standard gemological techniques.
Coral and CITES
CITES—The Convention on International Trade in Endangered Species (also known as the Washington Convention)—was established in 1975 and plays a crucial role in protecting biodiversity, contributing to the sustainability of the various industries that rely on biological resources.
There are three levels of protection in CITES:
Appendix I (species that cannot be traded internationally for primarily commercial purposes, unless permitted in exceptional circumstances); Appendix II (species that can be traded inter- nationally for commercial purposes, but within strict regulations, requiring determinations of sustainability and legality); and Appendix III (species included at the request of a country, which then needs the cooperation of other countries to help prevent illegal exploitation.
No species of precious coral is listed in Appendix I. Com- mon corals used for decoration or trinkets are listed in Appendix II, and include black coral (Antipatharia spp.), blue coral (Heliopora coerulea), stony coral (Scleractinia spp.), organ pipe coral (Tubiporidae spp.), fire coral (Milleporidae spp.) and lace coral (Stylasteridae spp.). A request from China in 2008 introduced some varieties of red and pink coral in Appendix III for trade monitoring, namely Corallium elatius, C. japonicum, C. konojoi and C. secundum.
The bulk of precious coral species are not listed in any CITES Appendix. Those not listed are the Sardinian coral (Corallium rubrum), garnet coral (Hemicorallium regale), deep sea coral (Hemicorallium laauense), misu coral (Hemicorallium sulcatum). A very abundant white common coral that is usually dyed as a precious coral imitation, the so-called Bamboo coral (Isidae family) isn't also listed in CITES.
Bellow a table with the correspondence between common trade name, scientific name, CITES listed taxonomy, and general facts and features of the main precious coral varieties (cf. CIBJO Blue Book 2020)
Fishing Regulations
Different countries have regulations for fishing coral and local laws apply in their jurisdiction. The main fishing areas include Taiwan, Japan, the Mediterranean and the Pacific islands, Hawaii and Midway. The latter two have very limited harvesting due to the high cost of deep sea operations.
In Taiwan, strict regulations have been implemented since February 2009 in order to preserve resources. Only vessels with coral fishery licenses are allowed to operate in five designated areas, and they must be fitted with Vessel Monitoring Systems, which report the location by the hour. There is a 220-day operation limit each year and an annual quota of 200 kg per vessel. Fishermen must record and submit fish- ery logbooks on a daily basis and are subject to random in- spections. If they fail to comply, their licenses will be revoked and never reissued. In 2009, there were 96 coral fishery licenses; currently there are 50. Coral boats, allowed to dock only at the Suao or Magoong, must notify the authorities before heading out and all harvests must be recorded in detail. In Japan, populations of local red coral (Corallium japoni- cum, also known as Paracorallium japonicum) were stud- ied in 2009, in both non-harvested and harvested areas off Amami Island in Southern Japan. In the harvested areas, the estimated average age of the coral populations is 10 to 20 years, contrasting with 20 to 40 years—and even 50 to 60 years—in non-harvested coral populations. Since the average age of commercially viable corals is 30 to 40 years, it was suggested that harvested populations may return to the pre-fishing level after at least 10 to 20 years of rest period. This study indicated that a rotational harvest would be useful for sustainable management.
In the Kochi Prefecture, a fishing permit is needed to har- vest coral (no new permits are being issued) during the two authorized fishing seasons from March to May and August to December and only in designated areas. After the nets are placed in the deep sea, the boat engines must be turned off to prevent dragging, thus minimizing possible damage to the seabed. Small specimens, sizes 3-7 cm, must be returned to the sea. Fishermen must also record their daily activities in a logbook, which is submitted to the proper authorities. A maxi- mum harvest of 750 kg of living coral is allowed per year. A different rule applies in Kagoshima and Okinawa, where the prefectural governments only allow fishing gear that can catch precious corals selectively, such as ROVs (Remotely Operated Vehicles).
In the Mediterranean, the General Fisheries Commission for the Mediterranean (GFCM) is a regional fisheries man- agement organization established under the FAO (Food and Agricultural Organization of the United Nations) and has been involved in developing a Regional Management Plan for red coral. In 2011 and 2012, it was recommended to pro- hibit coral fishing at depths less than 50m, and that only scu- ba divers could conduct the harvest, keeping a daily record of all catches by area and depth. It was also recommended that the legal minimum trunk diameter for red coral be at least 7 mm (measured within 1cm from the base).
In 2014, GFCM members adopted a Guidelines document for the management of Mediterranean red coral populations in the Mediterranean as a transitional measure towards the adoption of a Regional Management Plan, currently in development. Members declared that this resource deserves specific research to fill in the important gaps in understand- ing the actual status in the region and proposed a series of priority lines of research. The GFCM recommendations must be adopted by each Mediterranean country, both in Europe and Africa. Only stricter measures may be implemented or maintained by a single country.
The hand of master Pasquale Nastri holding Corallium rubrum branches © Liverino 1894



As a natural harvested gem material, corals have been regulated and monitored to preserve biodiversity in the eco- systems where they thrive. As stated earlier, International bodies such as CITES and FAO, as well as sovereign au- thorities in many countries have contributed to coral protec- tion with regulations, both international and national. Among the objectives of the CIBJO Coral Book are to identify, ad- dress and tackle the challenges and concerns of the industry especially relating to sustainability and traceability.

In Japan, the Precious Coral Protection and Development Association and the Kuroshio Biological Research Founda- tion have been involved in one of the most interesting ini- tiatives on precious coral sustainability. In a protected zone around the Birou island, Kashiwajima in Koshi Prefecture, small Corallium japonicum branches were attached to 60-kg artificial reef growing blocks, and planted at a depth of 100m. The 3 to 5 year project is monitoring growth rates and so far, there has been encouraging recorded growth before and after transplant. The information collected by this prolonged project could serve as a basis for future reforesting of local sea beds in areas where harvesting is prohibited.

© Precious Coral Protection and Development Association and Kuroshio Biological Research Foundation

In Sardinia, Italy, a local Scuba Divers’ Association is pres- ently using ROVs, not to harvest the local Corallium rubrum, but to clean broken fishing nets from seabeds and to con- tribute to the repopulation of this precious coral in the area. It is also trying to make a point that, despite present regula- tions, the use of ROVs with an adequate legal framework could serve as a much safer and environmentally compliant method for Mediterranean coral harvesting. Scuba diving at depths of 50m and below is considered to be very risky.

CIBJO, an ECOSOC organization under the United Nations, is following these two initiatives, while also exploring possible cooperation with local projects for reef coral growth in hatcheries and re-plantation onsite, as is the case in Fiji where future actions are being considered. Although there are no precious corals in Fiji, participating in such initiatives sends a message on the importance of preserving the ma- rine environment.

CIBJO is also working with a carbon consultancy firm, Carbon-Expert, to encourage the coral industry to reduce carbon emissions, thus helping mitigate ocean acidification, which also has an impact on carbon-based biodiversity (i.e. shells, pearl-producing mollusks and coral).

It is generally recognized that more research should be conducted on precious corals. The gemological literature has very few papers on this subject, but fostering contacts with the scientific community may help the industry to implement measures that will help it exist in better harmony with current sustainability concerns.


Edited and extended from Galopim de Carvalho, Rui (2018), Precious Corals, InColor, Vol. 38, pp. 70-78


Back to blog