Garnet

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The beautiful colour of the mineral garnet appeals to the imagination of people. Or rather, the mineral group garnet. For centuries people have seen the beauty of the deep red stones. It was also one of the first minerals I had as a child, a garnet pendant.

Geology
If we call something ‘garnet’ in the mineral world, it is actually an umbrella name for a group of minerals that have more or less the same basic chemical formula, X3Y2(SiO4)3 in which X and Y represent different elements. The name garnet comes from the Latin word granatus, from granum, seed. This probably refers to the seed of the pomegranate, those seeds are dark red and resemble garnet crystals. The English garnet comes from the old English gernet, which has the same Latin root. To dive a bit deeper into that chemical aspect… garnets are nesosilicates. Silicate means that they are (partly) made of of silicon and oxygen atoms. Nesosilicates are made from silicate tetrahedrons. Clusters of 1 silicon atom with 4 oxygen atoms, SiO4 (with a single exception in this group of a rare variety with more oxygen atoms). Garnets have three of these silicate tetrahedrons in their crystal structure building blocks. With garnets, two different groups are recognized based on the other elements, the Y and X, in the mineral with three minerals in both groups.

garnet grid

garnet solid E
Garnet solid solution series

These are the generalized chemical formulas. Within these 6 minerals (end members) there are again variations that have their own name and chemical composition. These 6 types form series in which variations are possible, as seen in the picture above.

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Green demantoid garnet, Andradite variety, from the Ural Mountains

A fairly complex and variable group of minerals. Because the chemical composition is variable, the hardness is too. This varies from 6.5 to 7.5 on the Mohs hardness scale. Almandine is quite hard and fine-grained it is used as a blasting agent. The best known and most common form of growth is the dodecahedron, but sometimes you also see trapezoid. Garnets belong to the cubic crystal system.
The most common type of garnet is Almandine. You might know this type in garnet schist from Scotland, Norway and Austria or from the island Wrangell between Alaska and Russia. These are the typical red garnets, sometimes nicknamed ‘carbuncle’.

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Grossular garnet from Loanhead Quarry, Beith, Scotland

Garnet is not a rare mineral. You can find it in many places in Great Britain, especially in Scotland. There you can see it in quite a few different types of rock. Especially in the so-called ‘skarn’, a metamorphic rock with coarse crystals, in eclogite and in mica schist.

Nice to mention are the garnets that can be found on the beach at Elie Ness (Fife). These are Pyrope garnets, very small crystals of no more than 1-2 mm. They erode from local tuff outcrops on the beach, but were not formed in this rock. Research on these garnets has shown that they were formed at great depths in the earth’s crust, an estimated 60 kilometers deep.

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‘Elie rubies’, Pyrpe garnets from Elie Ness beach

During the Carboniferous period the area which is now East Scotland was an area with active volcanos. Where Elie lies, there was once a volcano. The lava from this volcano is the basalt we see today. The tuff that is deposited here as well was created by ash from this volcano. In this tuff you can find tiny pyroop garnets that were formed deep within the earth. They are so-called ‘xenocrysts’ in the tuff, crystals that were not formed in this matrix, but became part of it as already existing crystals. When you walk on Elie’s beach and take the time to sit on your knees and look closely in the sand, you can find them. These beautiful red stones are nicknamed ‘Elie Ruby’, but they are not real rubies. In Scotland, too, there are beaches on the Knoydart peninsula where the sand consists of millions of tiny garnets, known as garnet sand.

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Garnet sand from the Scottish Highlands

In England, garnets are rarer than in Scotland. In the 19th century in Cornwall some rocks with particularly beautiful Almandine garnets were found. But the description of the location and the credibility of this find is being questioned. In the Lake District, a number of Almandine garnet localities are known. Grossular garnets can be found in Cumbria, Devon and in Cornwall.

Andradite is also known from Cornwall and Cumbria. Spessartine can be found in Cornwall and Devon. From Wales, Andradite and Spessartine have been described. Uvarovite does not occur in the UK.

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Garnet (Grossular-Andradite series) from the Cairngorm Mountains

And even in the Netherlands garnet can be found. Like I wrote, it’s not a rare mineral. So in the countries around us it occurs in different places. As the Netherlands is in fact merely a delta from some of the major European rivers, the sand from, for example, the Rhine and the Meuse contains all types of minerals that originate in the areas where the river receives its water from. This why how ‘our’ fluvial sand contains garnet. Very small of course, sand grain size, but still. This sand can be found at a number of places along the coast, including Petten and Bergen aan Zee. Which does not mean that there is no garnet sand in river sand from other places, though. But there the concentration is less dense and therefore not so easy to see.

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Beach sand from Petten. Mostly quartz with two tiny granites in the centre. Photo kindly provided by Angelina den Held from http://www.angierocks.nl


History and folklore

Garnet has played a major role in history. I started this blog by saying that it is an attractive mineral … and has always been. For centuries people have felt attracted to the different types and colours of garnet. It has been found in Bronze Age tombs, in pyramids, in Roman tombs, in early Christian tombs, in Medieval tombs, in jewels for kings and emperors, and I could carry on like that for a while But since this is a blog about Great Britain, I want to limit myself to the UK, with a small sidestep to the Netherlands.

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A blood-red Almandine garnet

We know the story of Noah and the Ark from the Old Testament. Noah had a red stone, a ‘carbuncle’ that lit up the Ark in the 40 days that the sun didn’t shine because it kept raining. The word carbuncle is an old name for all kinds of red stones, but especially for beautiful dark red garnets. According to the Bible, the High priest of Israel also had a red garnet as the third stone on his breastplate. King Solomon is said to have carried garnets in battles to protect him from injury. The function of garnet as a protector is known from several historical sources. It was a beloved stone for soldiers, it would protect against nasty wounds. The link between the red colour of the stone and the colour of blood can be made according to some historians, as well as the link between the blood of Christ and the blood red colour of garnet. And it would not only protect against wounds, but also against poisoning it was said to be extremely effective. A tour through the collection of the British Museum shows a wide range of items made with or from garnets. The same goes for the collection of the National Museum of Antiquities in Leiden. There is a striking number of Roman and Asian seals carved from dark red garnet. Pliny the Elder called garnet Carbunculus alabandicus, fire stone from Alabanda (Turkey), which at the time was an important trading place where a lot of garnet from Asia were sold to European tradesmen. In addition to Asian garnets, many garnets from the Czech Republic also found their way to the various European trade routes. Garnet has been mined there since the Bronze Age. The Greek Theophrastus of Eresos called garnet Antrax, after the Greek word for coal. Aristotle compared the colour with that of fire. The name Pyrope for one of the varieties of garnet also means fire. In the Roman Mithras cult garnet played an important role and a ring with a garnet showed you had reached the highest rank.

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Seal carved from garnet, 2nd century AD Asia. © The trustees of the British Museum

For the Greek and Romans, the garnet was also the stone that symbolized love. The name garnet is, as already mentioned, derived from the word for pomegranate. The pomegranate is a love symbol from the myth of Persephone. Hades, God of the Underworld, had kidnapped her. Demeter, Persephone’s mother, wanted him to bring her daughter back to the land of the living. Hades agreed, but before she left he gave her pomegranate seeds to eat. This meant that she had to keep going back to Hades during the darkest months of the year.

After the fall of the Roman Empire, the fascination with garnets remained. The Germanic people loved this stone. The Anglo-Saxons made the most beautiful jewels, decorations on swords and buckles with garnet set in gold, the so-called cloisonné technique. This is best known from two of the most important archaeological finds in Britain from the last 100 years. The Sutton Hoo Ship Burial and the Staffordshire Hoard, both Anglo-Saxon treasures. The Anglo-Saxons most likely called garnet ϸone readan stan (a red stone)
Not only the Anglo-Saxons were fond of garnet. The Scandinavians, Frisians, Francs and Merovingians also frequently used the garnet to decorate weapons and in jewelery.
The French king Louis the 14th is said to have used a garnet in the hope that it would increase his potency.

Garnet also has a darker side. Where in most cases it was seen as a protective stone, the Burushu people used garnets as bullets in their slings. When the British arrived in Hunza, the Burushu people used garnets as ammunition. They took loose garnet crystals in their weapons to shoot at the British soldiers. A similar story exists about the Navajo, they can find pyrope garnets on ant hills (Ant Hill Garnets) because ants carry them out of the soil. These are said to have been used as bullets, but they are no thrustworthy sources confirming this. The idea behind the use of garnet would be that the wound caused by a red garnet would be more bloody than a normal wound.

Sutton Hoo and the Staffordshire Hoard
In 1939 a remarkable grave was uncovered at an Anglo-Saxon cemetery on an estate in Sutton, Suffolk. In a burial mound archaeologists found a complete ship with a wealth of grave gifts. It turned out to be a 7th century grave, approximately between 610 and 635. A body was not found, but later analyzes showed that it must have been there and had probably disappeared because of the acidity of the soil. Who was buried in the ship is still not clear. But most likely it was an Anglo-Saxon, East Anglian king. Various names have been suggested, including that of Rædwald, the most likely candidate. The most famous and iconic find in the grave was the famous helmet. In addition, an enormous amount of golden artifacts, many of them with garnet cloisonné, was found. A sword with a pommel made of garnets laid in gold, buckles, a purse lid, mantle pins, you name it. All made of gold and garnet. Part of the treasure can be seen in the Sutton Hoo visitor center (an absolute must to visit!). Another part is on display in the British Museum in London.

Sutton Hoo purse
Purse lid, Sutton Hoo. Gold and garnet. © The trustees of the British Museum

In 2009, a metal detectorist made a once in a lifetime discovery near Hammerwich, Staffordshire. He found a real treasure in a field. More than 3500 items of gold and silver were excavated, many of them inlaid with garnet. All objects date from the 6th and 7th century. Back then, Staffordshire belonged to the Anglo-Saxon kingdom of Mercia. This find caused quite a stir and made the news headlines. The pieces have since been purchased by the Birmingham Museum and Art Gallery and the Potteries Museum & Art Gallery in Hanley. Part of the hoard is permanently displayed in both museums. Research into the finds is still ongoing.

Staffordshire Hoard
A part of the Staffodshire Hoard. © Birmingham Museum

Similar finds of garnet cloisonné objects have been done in the Netherlands. During an excavation of the terp of Wijnaldum (Friesland), in Limburg, the grave field near Rhenen (Utrecht), Groningen and in many more places, fibulas, buckles, pins, beads, etc. with gold and garnet were found. Especially in Rhenen a striking number of objects inlaid with garnets have been found. The majority of the garnets are Almandien, demonstrated by XRF and PIXE research (Willemsen 2014). The famous ‘Fibula van Dorestad’ was made using the same technique. It has been possible to test whether the pieces of garnet that have been used in a certain object did come from the same stone. This appears not to be the case with Dutch finds, but with some of the British objects it has been found that in a some cases the same stone was used to cut more slices for one object.

Fibula van Dorestad
Dorestad fibula. © Rijksmuseum van Oudheden, Leiden

Research done on the garnets in the British and Dutch objects, complemented with similar finds from Germany and Scandinavia, show that the garnets originally came from Asia, more specifically from India and Sri Lanka. Over the Indian Ocean and the Red Sea, they found their way to trade posts in the Mediterranean during the 5th and 6th century, often former Roman ports. The gold also came to Europe along these routes. Additionally, there was a trade route over land (through current Syria to Constantinople) and over the Black Sea. After the 6th century the supply of stones came to a halt, so stones from old objects and ‘old’ gold were probably reused for new objects (Hamerow 2017). Bohemia became a new source for garnets. From the 8th century on, Swedish and Russian garnets were also used. A large-scale investigation is currently underway in which a few thousand garnet objects from Europe (Anglo-Saxon, Scandinavian, Frankish, Merovingian) are being investigated different aspects, including the origins and possible trade networks.

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Clasp, Sutton Hoo, © The trustees of the British Museum

Read more:
The Circulaton of Garnets in the North Sea Zone ca. 400-700, H. Hamerow, 2017

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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