Jewels belonging to an Indian royal family, including the ‘manga malai’ necklace are to be auctioned later this month.

The auction by Bonhams is part of its Indian and Islamic sale on Tuesday 19 April.

The family, who are based in the UK and wish to remain anonymous, will be parting with a number of treasures that have been in their possession for generations, including a South Indian marriage necklace, a jewel encrusted dagger, and extravagant princely jewels such as an emerald and diamond-set belt buckle.

The ‘manga malai’ necklace – one of the highlights of the collection – is composed of linked mango-shaped elements, lavishly set with rubies and diamonds, and estimated at £50,000-70,000. The ‘mango garland’ design is unique to southern India, where the mango is regarded as a symbol of love and fertility.

The ‘manga malai’ was worn by women at special occasions such as weddings and also by traditional temple dancers (known as ‘devadasi’ or servants of the god or goddess), who would dedicate their lives to the worship of temple deities in a manner akin to marriage. Similar necklaces can be found in the David Collection in Copenhagen and the Museum of Islamic Art in Doha.

A jewel-encrusted dagger, estimated at £30,000-50,000, is one of the highlights of the Bonhams sale The dagger is an impressive gem-set enamelled piece decorated with gold, rubies and diamonds.

The hilt is of a type rarely produced in Mughal India and finds comparison with 18th century Persian daggers of similar form.

It was probably made in Rajasthan, known for its royal workshops and enamelling centres carrying on the Mughal tradition of superlative quality enamelling.

There is a similarly decorated hilt in the Nasser D. Khalili Collection in London. Set with a formidable 17th century Ottoman double-edged watered steel blade, it is estimated at £30,000-50,000.

Also among the princely family’s treasures is a rare belt buckle set with emeralds and diamonds and estimated at £18,000-£25,000.

The front is set with precious stones and the reverse exquisitely enamelled in green and green colours with elegant floral motifs.

A delicate yet magnificent armband will also feature in the sale.

A central octagonal diamond is flanked by diamond-set motifs, with the reverse side decorated as attentively as the front with fine enamelling comprising gold scrolling floral motifs on a dark green background.

This delicate and quietly beautiful piece is estimated at £8,000-12,000.

“This is a treasure trove,” said Rukmani Kumari Rathore, specialist in Islamic and Indian art at Bonhams.

“They are magnificent examples of 18th and 19th century craftsmanship and provide a wonderful opportunity to purchase an heirloom once owned by Indian royalty.”