Researchers have uncovered evidence of a vast operation of Roman-era illegal silversmithing, thought to be the largest ever found at a Roman site in the UK.

The team is working on a 15-year project at the site at Grange Farm in Gillingham, Kent. They found 15 kilos of litharge, which is a lead oxide – and a by-product of silver extraction. The team believes the site might be an illegal silversmithing operation, or an operation possibly carried out by the Roman state. In Roman Britain in the 3rd and 4th centuries, taxation across the empire was based on gold and silver.

The archaeological team discovered a mausoleum on the site and thinks the settlement was occupied by a clan who also worked the land – the silversmithing took place at one end of the main building, with domestic use confined to the other end and fireplaces in the centre of the building. Graves uncovered at the site contained the remains of an elderly woman thought to have been either a clan leader or one of the elders of the clan. Her coffin was lined with lead and isotype tests on her teeth have suggested she was from the area.

Isotype testing is based on water supplies in a particular area that the subject would have consumed and these are revealed via hair or teeth. She was also found to have suffered from osteoarthritis, but was buried respectfully and is unlikely to have had worker status in the clan.

The mausoleum for the elderly woman was two storeys high, suggesting a person of high status and wealth. Another unusual feature of the construction was a plain, red, tessellated floor, which is deemed unusual in Roman Britain, says the team.

Extensive valuable jewellery has been found, including a gold filigree necklace and bracelet – and the team thinks the occupiers of the site might have made items like silver ingots.

The team also says that the mausoleum remained undisturbed until the 11th or 12th century, suggesting that Anglo-Saxons left the Roman mausoleum untouched. It is estimated that the mausoleum dates to the 5th century AD – Roman rule in Britain ended between 388 AD to 400AD ie at the beginning of the 5th century AD. The mausoleum was moved after the Domesday Book in 1086 AD to make way for a medieval manor house.

So far the team has found 453 Roman coins, 20,000 fragments of pottery (weighing a quarter of a ton) – and around 8,000 animal bones.

The excavation is being undertaken by Pre Construct Archaeology and a team from Newcastle University.

Senior lecturer in Roman Archaeology at Newcastle University, James Gerrard, said:

“Quite why people were refining silver from silver-rich base metal alloys is a mystery. Quite why people were refining silver from silver-rich base metal alloys is a mystery, too. They probably weren’t coins, as the bronze coinage had too little silver in it.

“We might expect that the refining of silver here was either being done officially by the ‘Roman state’, or perhaps illicitly. It’s an unusual aspect to the site.”

The team has produced a 200-page study By the Medway Marsh, detailing the excavation and finds.

You can read more about the excavation at Kent Online.

Images by Pre-construct Archaeology.