A private collection of precious gemstones thought to be the largest in the UK is to be sold at auction.

The collection of more than 680 stones includes some of the world’s rarest and purest rubies, emeralds, tanzanites and sapphires and is valued at more than £8 million, auctioneer John Pye’s luxury assets division said.

The collection ranges from an 8.96 carat pink topaz ring estimated to be worth £600 to a matching set of 35 carat Zambian emerald earrings valued at between £500,000 and £600,000.

Tanzanite gemstone set in 18 carat white gold mounted with diamonds. Photos: Nick Ansell/PA Wire

The UK-based anonymous collector ethically sourced the stones directly from mines in countries including Burma, Sri Lanka, Tanzania and Zambia over the last 40 years.

All the stones were originally sourced as loose gems and had only recently been set and mounted against diamonds into pieces of fine jewellery to showcase their desirability. Named the David Jerome Collection by the collector, the stones will go on sale at a series of online international auctions.

John Pye said the increasing value of coloured gemstones was now outstripping diamonds.

Interest rose significantly after the Duchess of Cambridge began wearing her sapphire and diamond engagement ring.

In a statement released through John Pye, the owner said he was not sorry to see his years-long collection being broken up.

We believe the collection to be certainly the largest in the UK, if not Europe

“I am an avid collector and I love sparkly things. I started my collection with a tanzanite. I began to search for the best available stones and I learned all about them.

“I love the buying, the finding of the mine and acquiring the very best stones. The best mines from all over the world come directly to me with their finest stones.

“We are giving people the opportunity to buy the most beautiful stones in the world, just as nature created them.

“I am now happy for the stones to be sold so other people can enjoy them as much as I have.”

John Pye gemstone valuer Ian Hall said: “This is quite simply a once-in-a-lifetime opportunity to buy from an exquisite and extremely valuable collection of gemstones.

“We believe the collection to be certainly the largest in the UK, if not Europe.

“Every gemstone in the collection has its own independently-issued certificate, a guarantee of both authenticity and quality, including GemResearch Swisslab (GRS) certificates showing that they are the purest quality in their natural form.”

The first auction in September will offer 345 gemstones from the collection.