Agates

The first in a series of scribbles from my Jewels notebooks.

A sliver of agate. PHOTO: CREATIVE COMMONS Cobalt123

“I was busy with a single art, that of a small, unpopular theatre; and this art may well seem to practical men busy with some programme of industrial or political regeneration – and in Ireland we have many excellent programmes – of no more account than the shaping of an agate; and yet in the shaping of an agate, whether in the cutting or in the making of the design, one discovers, if one have a speculative mind, thoughts that seem important and principles that may be applied to life itself. Certainly if one does not believe so, one is but a poor cutter of so hard a stone.” Yeats 1919.  The Cutting of an Agate.

WHAT STORIES WOULD I HAVE TOLD ABOUT AGATES IF THEY HAD THEIR CHAPTER?

  1. Agates are named after the Achates river in Sicily, now called the Drillo (from Theophrastus) so it would be interesting to see what kind of agates are found near the Drillo and whether they are somehow more beautiful, or common, or special than those found in other places.
  2. DH Edwards in Among the Fisher Folk of Usan and Ferryden 1921 talks about the “pebble house”. “We have on many occasions engaged in the work of “hauking” pebbles from the rocks at Usan and have several specially finely marked specimens. Many of the visitors have been very lucky hunters and possess well-polished stones set in brooches, pendants, sleeve-links and ear-rings. The salmon fishers also secure not a few, one of these men having a complete outfit for cutting and polishing the stones in a snug little workshop attached to his bothy at Marywell…
  3. That the work was engaged in with success about one hundred years ago is proved by the ruins of the cottage already spoken of as still to be seen “along the braes” known as the “pebble hoose”. In this humble and lonely abode, almost washed by the sea, a man lived by himself and worked as a lapidary. “We believe specimens of his handicraft are to be seen in several mansions in this district – notably in Usan House, the top of a round table formed with stones of many colours, and set with fine taste and skill.” P67
  4. “Harry Scott of Edinburgh searched for and collected St Cyrus agates for more than twenty years. Some of these he collected below high vertical cliff faces, although he frequently warned young collectors about the obvious dangers inherent in such a practice. Sadly, whilst on a collecting trip in an area where he had discovered large agates of superb quality, the dangers became all too apparent as while hammering at and below a vertical cliff face, he loosened two or three tons of rock which fell on him, killing him instantly.”
  5. Wonderful names of agates – “rubber lips” or “rising sun”…
  6. THE MYSTERY OF MIDDLEFIELD FARM , 1.5KM NORTHEAST OF CUPAR: agates in brilliant yellow and red colours have been found in small numbers on the fields of the farm which is situated on sandstone rocks, so the agates are clearly not of local origin. They are quite different from most Scottish agates and are highly sought after.
  7. The big European centre was Idar-Oberstein 130 km SW of Frankfurt. Thousands of people were employed as gem cutters, until local supplies began to run out c.1860 and they looked to Uruguay and Brazil.
  8. P63: Pebble jewellery in vogue because Queen V loved Balmoral. On September 6 1850 she climbed Beinn à Bhuird, 30km west of Balmoral and found several cairngorm crystals (brown transparent quartz) which she recorded inLeaves from the Journal of our Life in the Highlands 1968.
  9. The last lapidary from the old school in Edinburgh was Alexander Begbie who died in 1958. He was 83.

WHAT QUALITIES DO THEY HAVE?

Marbodus, the 11th century Bishop of Rennes, believed agates made their wearers agreeable and persuasive…

Pliny wrote that it was a mark of high prestige to own an agate cup… agates had power to cure the poisonous stings of certain spiders, to make a wrestler invincible or to turn away storms.

For epilepsy or sleepwalking put the agate in water when the moon is full, leave it for three days, then on the fourth remove it and use the water for cooking all your food. The Lapidary Journal suggests this comes from the history of using agate pestles and mortars for grinding drugs, chemicals and spices to powder. Pliny mentions the first of these and chemists still use agate for grinding chemicals today. A gourmet shop in Berkeley used to sell agate mortars and pestles to cooks for grinding herbs and spices…

WHAT ARE THEY?

They are varieties of quartz (silicon plus oxygen).

WHO WAS THE MOST FAMOUS COLLECTOR?

Matthew Forster Heddle, Professor of Chemistry at St Andrews from 1862-84 had the best 19th century collection in Britain.


WHERE ARE THEY FOUND?

The most famous agate locality in Britain was the Blue Hole, Usan (3km south of Montrose, near Usan House, now covered over).

The largest agate bearing rocks are in the mountains of southern Brazil, stretching 600 km to Salto on the Uruguay River.

They usually occupy the sites of former gas cavities in basalt and andesite, occasionally can fill other kinds of cavities and fissures (vein agate). They can vary in the amounts of quartz present… may consist just of chalcedony (fine grained quartz) or carnelian, jasper, amethyst, smoky quartz, common quartz. Most British agates are found in the Old Red Sandstone lavas in the Midland Valley of Scotland where thin lava flows issued from scattered volcanic centres. later they were weathered, breaking down into soft rock or soil, then volcanoes became active again with new lava flows covering it… “the formation of lava flows and the formation of agates are not contemporaneous or even connected events… agates do not form in the final cooling stages of volcanic rocks as has often been assumed” What is believed to happen is that once the flows have cooled and buried 100meters or so underground, silica solutions penetrate them, filling them with agate forming material…

HOW CAN YOU FIND THEM?

Lelande Quick in The book of agates 1963 wrote that rockhounding was born of the 1930s Depression when people tramped California looking for gold, and found petrified wood and interesting rocks which they marketed as “Indian jewelry” – he also wrote that in 1959 the US Bureau of Mines estimated there were 3 million amateur rock collectors in the United States… Magazines were written for them – Rocks and Minerals began in 1926 and is still being published today. HIS TIPS:

  • contact the nearest natural history museum and ask to see specimens of raw, uncut agates.
  • get precise details of an occurrence. Use a good map.
  • bring two hammers, 1kg and 2kg, one or two cold chisels of different weights, an eye lens of 10x magnifications, bags and a rucksack. Possibly also crowbar, pick aze and sledgehammer.

Castellani, Augusto. Gems: Notes and Extracts.Trans. Mrs John Brogden. London: Bell & Daldy, 1871.

  • Ear agates are the parts of the stone where, in the cutting, are discovered circular bands, small in diameter, arranged with regularity abut one spot. The first round is white, the second is black, green, red, blue or yellow
  • Figured agates do not exist in a natural state… the skilful artist often finds it necessary to cut away some lines, marks or spots… no little study and cleverness are required (p.24)
  • Camello Leonardo da Pesaro has seen one with seven trees on an even ground; Boece de Boot had seen one with a mitred bishop; Poujet had seen one with a Turk. You can stain agates artificially – black is given by boiling the stone in honey, olive oil or sugared water and afterwards in sulphuric acid which carbonizes the oil and sugar absorbed by the stone. For blue you could use yellow prussiate of potassium with protoxide of iron.

Please note that these are just random notes that I typed in very quickly one day in a library, or on a plane. They are here for interest, or a prompt to researchers about where to look… but if I had actually used them in my books I would have checked them carefully.

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