Mudlarking: The Mystery of the Thames Garnets

By Jason Sandy

Why are semi-precious gemstones lying on the bottom of the River Thames in London?

Has a jewelry heist gone terribly wrong? No one knows, but each year mudlarks find hundreds of red garnets in several locations along the exposed riverbed at low tide.

Anglo-Saxon jewelry from Sutton Hoo burial, England

Anglo-Saxon jewelry from Sutton Hoo burial, England British Museum)

For millennia, garnets have been used in jewelry and to decorate precious objects. The Anglo-Saxons, who lived in England from the 5th - 11th centuries, especially loved garnets and inlaid the semi-precious gemstones in a wide variety of prestige objects, from sword pommels to fine jewelry as illustrated in the incredible artefacts recovered from the Sutton Hoo ship burial and Staffordshire Hoard.

Anglo-Saxon brooch from Covent Garden,  London

Anglo-Saxon brooch from Covent Garden, London (Jason Sandy)

The garnets have been cut into thin, transparent slices and fitted into individual cells using the cloisonné technique, backed with gold foil of intricate patterns of lines and indentations to enhance the brilliance of the stones. In London, a 7th-century Anglo-Saxon brooch was discovered in a woman’s grave in Covent Garden, now on display in the Museum of London. It is decorated with twisted gold filigree on gold plates and inlaid with a mosaic of polished, red garnets. According to the Museum of London, this rare type of brooch was “fashionable among aristocratic Anglo-Saxon ladies,” and the woman who wore it could have been “of noble, possibly even royal, birth.”

garnets found in the thames river in london

Thames garnets (Jason Sandy)

When the tide recedes in Central London, vibrant red garnets glisten like pomegranate seeds (from which their name originates) in the sunlight as they lay clustered on the surface of the exposed riverbed.

Gold ring with red garnet

Gold ring with red garnet (Anna Borzello)

“There is something magical about picking garnets from the riverside grit,” explains mudlark Anna Borzello. “They are tiny, red and satisfyingly faceted. Best of all, they are such an unlikely find in Central London.”

Mudlark Florence Evans describes the thrill of gem hunting, “Garnets make me think of India, exotic trade, and treasure; finding them in the Thames seems so incongruous - magical in fact. Mudlarking for me is very much a treasure hunt and garnets are gems after all!”

No one knows exactly where the garnets are from or how they ended up at the bottom of the River Thames. Robin Hansen, curator at the Natural History Museum in London, confirmed that garnets are not native to the Thames; they were deposited there by people. But why? There are many theories, but there is still no conclusive evidence to solve the mystery. Alan Murphy, who has been mudlarking for over 30 years and has collected hundreds of garnets, believes that “they are Almandine garnets from India or South Asia, brought to London via the trade routes of the British East India Company.” Alan explains that possibly “while hessian sacks of garnets were being unloaded from ships, unscrupulous characters could have thrown some overboard to return at low tide to retrieve them to sell in the many inns along the Thames.”

Hazel Forsyth, a senior curator at the Museum of London who has extensively researched gemstones and has written a book about the Cheapside Hoard jewels, believes that, “the garnets’ presence on the foreshore is probably due to accidental loss of a shipboard consignment.” She believes that some of the Thames garnets could have been intended for jewelry making before they were lost in the river.

To assess whether the Thames garnets are jewelry grade gemstones, I sent some of them to Kit Casati, a jewelry designer in the United States. He has kindly conducted several tests and cut some of the Thames garnets in a “cabochon” style with a diamond saw and diamond-plated wheels. Kit confirmed that some of the garnets from the Thames are large enough and of sufficient quality to be cut and set in jewelry.

With a hardness of 7.5 on the Mohs Scale, garnets are also used as an abrasive agent in industrial applications. Once the garnets have been crushed into finer grains, they can be used for sand blasting, water jet cutting, polishing, lapping, and even for cutting steel. For centuries, many industries and their workshops were located along the River Thames. Based on the industrial locations along the Thames were garnets are found, it is possible that they are a by-product or waste from industrial use. But, many of the larger, uncrushed garnets could not have been used for these abrasive purposes.

Shrouded in mystery and intrigue, the garnets are a highly desirable mudlarking find on the Thames foreshore. “I like the fact that no one knows for certain how they ended up on the foreshore, and that the most likely theories link them to London’s ship-building past,” explains Anna Borzello. “I mudlark all the time, and I love wearing something that I’ve found and that links me to the river.” Many mudlarks have commissioned jewelry designers to set the rough, uncut garnets into rings and jewelry. Hannah Upritchard, a jewelry designer in East London, has created several Thames garnet rings for Anna and other mudlarks.

Silver garnet-set rings set on top of the large garnet

Silver garnet-set rings set on top of the large garnet (Florence Evans)

Several years ago, a three-year-old girl discovered one of the largest red garnets (her birthstone) while mudlarking with her mother, Florence Evans. It’s a whopping 1 1/4 inch in length. Florence says that “it’s currently on display in my daughter’s bedroom. We enjoy holding and turning it in our hands. When my daughter is older perhaps she will want to set it. Whatever she chooses, I hope she will always treasure it as she does now!” Florence has commissioned Nicolette Parker, a London based jewelry designer, to make rings from the smaller garnets she has found in the Thames.

Victorian ring with red garnets found in the Thames

Victorian ring with red garnets found in the Thames (Jason Sandy)

In 2017 I posted a photo on Instagram of some Thames garnets and a 19th century Victorian garnet-set ring I had found on the Thames foreshore. Kit Casati saw my post and contacted me. “I was fascinated with the history and journey that these raw garnets must have made to end up where they did, before Jason discovered them,” explained Kit. “I am always amazed at the natural growth patterns of minerals as they form in their various crystalline structures. To me, they are the Earth’s sacred geometry that has been frozen in time. Garnets are one of my favorite gemstones.”

thames garnet pendant

Glowing effect of the red garnets (Kit Casati)

Kit, who has designed and produced jewelry for numerous Hollywood actors, kindly offered to make a pendant for my daughter if I sent him some of the Thames garnets. I was very touched by his kind gesture and sent him (a complete stranger) a packet of 25 garnets which my daughter had found in the Thames. I wasn’t sure what to expect, but I received a return package in the mail 9 months later. My daughter was delighted to see her returned garnets set in a stunning silver pendant. To enhance the appearance of the garnets, Kit cleverly placed them in silver loops so that light can pass through the gemstones from both directions.

Silver ring with red garnet (photo © Alan Murphy)

Silver ring with red garnet (Alan Murphy)

Garnets are considered by many people to have special powers. Alan Murphy explains that a garnet is “intimately tied to the Earth, and is a talisman of protection and unyielding strength, both physically and intellectually. Its energy helps alleviate worry, panic, fear, and assists in maintaining a calm connection to the present. It allows one to perceive the absolute support of the Universe.” Because his wife suffers from Lupus SLE, Alan says that he “decided to help her by using a garnet she could wear as a talisman to help heal her pain and help protect her both physically and intellectually while I’m not with her.” The biggest garnet Alan has found is now mounted in a medieval-style silver ring which was designed and produced by Hannah Upritchard.

Although their origins and use remain unknown, red garnets are an intriguing and magical find from the River Thames. Their raw, deep red appearance and intrinsic beauty have inspired jewelry designers in the US and UK to create stunning rings, pendants, and other items using the historic garnets retrieved from the muddy river bed. The powerful garnets are also being used as talismans by people suffering from illness who call upon the healing powers of the garnets. But for now, the red garnets in the River Thames will remain an unsolved mystery.

Mudlarking on the Thames Foreshore requires a permit. Learn about rules for mudlarking in London ›

Jason Sandy shares some of his best mudlarking treasures


Learn more about mudlarking


Learn more about the experiences of mudlarks, who search the shores of rivers, bays, and seas for historical finds and other objectsArticles ›

This article appeared in the Glassing Magazine July/August 2018 issue.

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Has anyone thought of checking through the Lloyds of London records? If they were the result of an accidental loss, the company may have made an insurance claim on them.

Brendan February 28, 2023

Are the Thames garnets for sale?
I live in the US.

Bambi Prochnicki February 22, 2022

Please let me know if any loose gatnets are for sale! This looks like fun but no place to practice in Kansas.

Darcy R Smith September 27, 2021

I live in the southern United States. Do you know if there are any mudlarking groups in the U.S.?

Mary April 19, 2020

I had no idea about mudlarking. I am so intrigued and want to learn more!

Jill Martin January 14, 2020

Such a terrific mysterious situation!! So much fun!!

ConCon October 28, 2019

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