The office of the country’s president, Hery Rajaonarimampianina, posted the first image of divers recovering a hulk of silver on its official Twitter account on Thursday. “The discovery of a wreck and treasure in the waters,” read the message in French and Malagasy.
A joint UK-US archaeological research mission found the 55kg bar of silver in shallow waters off Saint Marie island, the office said.
The team in Madagascar was led by Barry Clifford, an underwater investigator who in 2000 discovered some remains of William Kidd’s ship, Adventure Galley, including a metal oarlock, shards of Ming porcelain and bottles of rum three centuries old.
The president’s office said the silver may be part of a treasure haul belonging to Kidd from the same ship.
The bar is imprinted with a T and an S as well as other smaller carvings of numbers. Soldiers have been guarding it since it was brought ashore by divers.
Rajaonarimampianina was presented with the bar at a ceremony on Thursday attended by British and US diplomats, which the president’s office said was a “symbolic” gesture.
Timothy Smart, the British ambassador to Madagascar, told the BBC he hoped the discovery of the treasure would boost Madagascar’s tourism industry because of interest in Kidd.
The son of a Presbyterian minister, Kidd was a buccaneer and a captain for a private British ship in the Caribbean for some years, but it is claimed he decided that he found piracy more rewarding after he was commissioned to sail to Madagascar on the Adventure Galley.
His most famous capture was a 400-tonne ship, the Quedah Merchant, which carried silver as well as silk, gold, sugar, opium and cloth.
Some modern historians have disputed his reputation as a pirate, claiming Kidd was only ever a wronged privateer who believed he was authorised by the government to attack foreign vessels.
Captured in Boston in 1699, where the governor had promised him clemency, he was sent to Newgate prison. The jewels found on his ship were valued at £30,000 – the equivalent of around £10m today. But the remainder of his treasure was never found.
At Kidd’s execution for piracy in 1701, the hangman’s rope snapped and he fell to the ground still alive. A chaplain said the prayers again, Kidd was led up the steps of the gallows for a second time and the rope held.