On Wednesday, a cache of dazzling jewels linked to the Buddha’s mortal remains, which have been hailed as one of the most astonishing archaeological finds of the modern era, will go under the hammer at Sotheby’s in Hong Kong.

For over a century these relics, unearthed from a dusty mound in northern India in 1898, have sat largely unseen, cradled by a private British collection.

Now, as the gems prepare to leave the custody of their keepers, they are stirring not just collectors’ appetites but also some unease.

They come from a glittering hoard of nearly 1,800 pearls, rubies, topaz, sapphires, and patterned gold sheets, first glimpsed deep inside a brick chamber near the Buddha’s birthplace in present-day Uttar Pradesh in India.

Their discovery – alongside bone fragments identified by an inscribed urn as belonging to the Buddha himself – reverberated through the world of archaeology. Nicolas Chow, chairman of Sotheby’s Asia and worldwide head of Asian Art, believes this is “among the most extraordinary archaeological discoveries of all time”.

Yet as these relics now face the glare of the auction room, experts tell the BBC that a question hangs heavy: can the sale of treasures so intimately woven into India’s sacred past be considered ethical?

In 1898, William Claxton Peppé, an English estate manager, excavated a stupa at Piprahwa, just south of Lumbini, where the Buddha is believed to have been born. He uncovered relics inscribed and consecrated nearly 2,000 years ago.

Historians agree these relics, intact until then, are the heritage of both the Buddha’s Sakya clan descendants and Buddhists worldwide. The bone relics have since been distributed to countries such as Thailand, Sri Lanka and Myanmar, where they continue to be venerated.

“Are the relics of the Buddha a commodity that can be treated like a work of art to be sold on the market?” wonders Naman Ahuja, a Delhi-based art historian. “And since they aren’t, how is the seller ethically authorised to auction them?

“Since the seller is termed the ‘custodian’, I would like to ask – custodian on whose behalf? Does custodianship permit them now to sell these relics?”

Chris Peppé, great-grandson of William, told the BBC the family looked into donating the relics, but all options presented problems and an auction seemed the “fairest and most transparent way to transfer these relics to Buddhists”.

Julian King, Sotheby’s international specialist and head of sale, Himalayan Art, New York told the BBC the auction house had made a thorough review of the jewels.

“As is the case with any important items and collectibles that are offered for sale at Sotheby’s, we conducted requisite due diligence, including in relation to authenticity and provenance, legality and other considerations in line with our policies and industry standards for artworks and treasures,” King said.

Ashley Thompson, of Soas University of London, and curator Conan Cheong, both experts in Southeast Asian art, have more questions. In a joint statement they told the BBC: “Other ethical questions raised by the sale are: should human remains be traded? And who gets to decide what are human remains or not? For many Buddhist practitioners around the world, the gems on sale are part and parcel of the bones and ash.”

The sale of the relics has also sparked concern among Buddhist leaders.

“The Buddha teaches us not to take other people’s possessions without permission,” Amal Abeyawardene of London-based British MahaBodhi Society, told the BBC. “Historical records indicate that the Sakyamuni clan were granted custody of these relics, as the Buddha emanated from their community. Their wish was for these relics to be preserved alongside adornments, such as these gems, so that they may be venerated in perpetuity by the Buddha’s followers.”

Chris Peppé has written that the jewels passed from his great-uncle to his cousin, and in 2013 came to him and two other cousins. That’s when he began researching their discovery by his great-grandfather.

The Los Angeles-based television director and film editor wrote he had found 1898 newspaper reports – from Reuters to the New York Tribune – announcing the find of Buddha’s remains.

“The colonisation of India by the British had been a source of some cultural shame for me [and continues to be] but, amidst the treasure hunters who hauled their finds back to England, there had also been people focused on the pursuit of knowledge,” Chris Peppé writes.

He noted his research revealed a lot about his ancestors who he had dismissed as “prejudiced Victorians from a bygone era”.

“I learned that Willie Peppé’s first wife chose to travel around India for her honeymoon and loved the country and its culture. Sadly, she died from an unspecified illness. I learned that my grandmother was outraged at the land laws that applied to Indian women.

“And I learned that the excavation of the stupa was an attempt by Willie Peppé to provide work for his tenant farmers who had fallen victim to the famine of 1897.”

He writes his great-grandfather’s “technical diagrams of ramps and pulleys suggest that he was also a trained engineer who couldn’t resist a project”.

William Peppé handed the gems, relics and reliquaries to the colonial Indian government: the bone relics went to the Buddhist King of Siam (Rama V). Five relic urns, a stone chest and most other relics were sent to the Indian Museum in Kolkata – then the Imperial Museum of Calcutta.

Only a small “portion of duplicates”, which he was allowed to keep, remained in the Peppé family, he notes. (Sotheby’s notes say Peppé was allowed to keep approximately one-fifth of the discovery.)

Sources told the BBC the auction house considers the “duplicates” to be original items considered surplus to those donated, which the “Indian government permitted Peppé to retain”.

Over the past six years years, the gems have featured in major exhibitions, including one at The Met in 2023. The Peppé family has also launched a website to “share our research”.

Some scholars argue Buddha relics should never be treated as market commodities.

“The Sotheby’s auction transforms these highly sacred materials into saleable objects, in continuation of acts of colonial violence which extracted them from a stupa and called them ‘gems’ and ‘objects of interest to Europeans’, creating a false division with the ash and bone fragments they were consecrated with,” say Thompson and Cheong.

Chris Peppé told the BBC that in all the monasteries he had visited “no Buddhists regard these as corporeal relics”.

“A few Buddhist academics at western universities have recently offered a convoluted, fact-defying logic whereby they may be regarded as such. It’s an academic construct that is not shared by Buddhists in general who are familiar with the details of the find,” he said.

Peppé said the family “looked into donation [of the relics] to temples and museums and they all presented different problems on closer scrutiny”.

“An auction seems the fairest and most transparent way to transfer these relics to Buddhists and we are confident that Sotheby’s will achieve that.”

Some also point to The Koh-i-Noor, seized by the British East India Company and now part of the Crown Jewels, with many Indians viewing it as stolen. Should the Buddha’s jewels be next?

“Repatriation, I believe, is seldom necessary,” says Ahuja. “Such rare and sacred relics that are unique and which define a land’s cultural history, however, deserve the government’s exceptional attention.”