About agate – who knew!

When PGG started in 2007 we used, out of necessity, a lot of stones that Polly had in stock already from long ago, or we bought quite inexpensive stones to start off with till we saw how it went.  Among these were some flat faceted beads of banded agate and I confess that at the time, while I did acknowledge that the patterns were astonishing, the colours were very muted and they didn’t do much for me, and I thought that was all there was to agate – nice but nothing special. Huh. Shows what I know.

The reason I’m thinking about agate at the moment is because we’ve just been given a really wonderful commission for a Roman intaglio ring, the intaglio to be carved in green agate. We easily found the prefect stone for the job but far from being muted and pale, it’s the most incredible dark green, and flawless, quite the opposite of the first agate beads we used. It struck me as interesting that the same stone could be so different, so I went on a bit of a dig for knowledge…

Like most gems, agate has been used for thousands of years, not only in adornment but as tools and vessels as well because it is plentiful, it’s hard and carveable, and it takes the most wonderful shine. The oldest pieces of carved agate, dating back to the bronze age, were found in Crete which is where agate was actually first found. It was named after the river on whose banks it was found – the Achates – by philosopher and naturalist Theophrastus in about the 3rd century BC. The Holy Grail of Valencia is carved in red agate, but it’s only the agate cup that is thought to have been carved in the time of Christ and the elaborately decorated stand was added much later. The Romans loved carving agate – hence the very familiar intaglio seal rings – and it makes the best cameos too because of the layers of colour which are purer and much more long lasting than cameos carved out of shells. And agate has even been used in buildings; the Agate Rooms in Russia were the dream of the Catherine II and the genius of a Scotsman called Charles Cameron, employed by Catherine to make the rooms for her. I had absolutely no idea that agate was so versatile – the things you learn!

Because agate is found all over the world – including Antarctica! – it comes in the most diverse colours and patterns and it seems that everywhere that produces it calls it by their own name, so there are literally hundreds of ‘different’ agates. Botswana agate, for example, is reallly a banded agate, but is distinguishable by its pink hues which have made it famous and worthy of its own name. In truth most agates belong to one or other of the several families of agate and are simply found in varying patterns and colours. A simplified version of the groups of agate is: moss agate, banded agate, lace agate, dendritic agate, fire agate and iris – or rainbow – agate, and as they’re all so different they all deserve a quick look.

Agate is chalcedony (kal-seh-duh-nee) and quartz and is mostly formed in volcanic and metamorphic rocks which means that there is plenty of opportunity for the agate to be coloured by different minerals and formed by different geological events.

Moss agate, the first on the list, is called this because oxides of iron and manganese get embedded in the chalcedony and form moss like inclusions in the rock. There isn’t any vegetation involved, in spite of appearances, and it is found mainly in North and South America, India and and Europe and is usually formed in volcanic rocks. It looks fabulous in jewellery.

Banded agate, the one with which we are all probably the most familiar, is also a volcanic byproduct, consisting of microscopic quartz crystals formed from layers of deposited silica in volcanic cavities. Banded agate forms some of the most exotic and colourful patterns and this is probably because it’s found all over the world in different geological situations.

Lace agate comes in two varieties; blue lace agate found in Africa (mostly Namibia)  is particularly hard. Crazy lace agate is found in northern Mexico and comes in stunning patterns, usually red and white and yellow.

Dendritic agate, from the Greek word dendrites meaning tree-like, is sort of along the same lines as moss agate only is much more dramatic, sometimes forming whole miniature scenes. For obvious reasons good pieces of dendritic agate are highly collectible. Like moss agate, dendritic agate is found almost all over the world, but the most notable pieces apparently come from Crete.

 

And then we come to the two most extraordinary, surprising agates, about which I knew absolutely nothing, including that they even existed! The first is rainbow – or iris – agate. This is really a banded agate, but in order to see the rainbow it needs to be cut very thinly so that the stone can be lit from behind to enhance the rainbow. It’s not a rare agate really, and it is used mostly either displayed with a light behind it, or for metaphysical properties. It is absolutely beautiful.

And last but by no means least is fire agate. This is found only in the southwestern United States and in Mexico, and was formed millions of years ago when that part of the world experienced massive volcanic activity. Hot water, which was saturated with silica and iron oxide, repeatedly filled bubbles and cracks in the rock, building up layer upon layer and creating the vibrant iridescence. This agate is rare and precious – and I really, really want to see one!

I’ve been amazed to discover all this about the humble agate, but what has surprised me most is realising that this dedicated magpie really missed a trick by paying it so little attention all these years, but not any more!

 

 

 

 

4 thoughts on “About agate – who knew!”

  1. What a brilliant and interesting journey you have taken me on with agate. I am always astonished at dendritic agates and have seen a couple of wonderful “landscapes “ I’d love to get some moss agate, green is my colour, I’d love a beautiful dark green stone like the one you have for your ring! It would be fantastic to see a piece of iris and fire agate. Who knew these beauties were even around.
    Such a wonderful stone to work with. Even being able to carve it.
    How very exciting.

  2. I can easily get you a piece of the green agate, just say the word! I’m glad you enjoyed it, it was a fun write.

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