วัสดุปะการังแดงRed coral珊瑚

Coral's amulet career runs on two things: it is red, and it comes out of the sea already branched. In southern Italy the cornicello, the little twisted horn worn against the malocchio, is carved from red coral as often as it is cast in gold or silver, and the coral is read as sacred to Venus. In Puerto Rico the azabache bracelet — the commonest protection put on a child there — carries a black or red coral amulet in the shape of a fist with the index-finger knuckle protruding. In Alsace, southern Germany and Switzerland, Jewish boys wore textile neckbands for their brit milah with a coin or a piece of coloured coral set in the middle, to draw the evil eye away from the child during the circumcision; the practice continued into the early twentieth century.

At the other end of the network, coral is court material. Chinese writing has long associated red coral with auspiciousness and longevity, for its colour and its resemblance to deer antlers. It peaked under the Qing, when it was almost exclusively reserved for the emperor, worked into coral beads for court jewellery, often with pearls, or into decorative miniature trees. The Qianlong Emperor established a code in 1759 setting strict rules for its use. The route that supplied it is named: an early-modern coral network beginning in the Mediterranean and reaching Qing China through the English East India Company.

By the middle of the nineteenth century coral fisheries were working the Mediterranean, the Red Sea and the Persian Gulf. The gear is described plainly: two heavy wooden beams crossed at right angles, weighted with stones, netting slung beneath, lowered on a strong rope over an outcrop and dragged by the boat until the coral breaks off into the net.

Intensely red coral is still prized as a gemstone, and it is now scarce. Writers on coral say why in the same breath: red coral is very rare because of overharvesting, and giving coral as a gift is inadvisable while corals are in decline from climate change, pollution and unsustainable fishing. A charm cut from a reef animal is the clearest case in this atlas of a material whose supply is a live argument, and the argument is not about amulets.