Half a century before California was flooded with wild-eyed prospectors, Ireland experienced its own gold rush, just south of Avoca in County Wicklow. The trigger was a local schoolmaster who – curious neighbours couldn’t help but notice – was living beyond his means. It turned out he was panning the local river sands for grains of gold, which he quietly sold to Dublin jewellers. But if there was gold in the river, where did it come from? Years of fruitless searching for the “mother lode”, the bedrock source of Wicklow’s alluvial gold, were to follow. Two centuries on, two British geologists reckon they can explain why no one has ever found it.
THE rumours started in the summer of 1795: in County Wicklow in the south-east of Ireland a local schoolmaster by the name of Dunaghoo had discovered gold in the Aughatinavought river. By early September, word had spread and hundreds of the schoolmaster’s neighbours abandoned their harvest work. Armed with frying skillets and kitchen pans, they joined the throng along what came to be known as Gold Mines River. The luckiest prospectors positioned themselves at the richest site, about a kilometre below Ballinagore bridge, dubbed the Red Hole on account of its red-stained sediments.
In six weeks, the miners recovered an incredible 80 kilograms of gold. Fabulous riches were there for the taking, or so everyone hoped. And indeed, before the year was out the “Wicklow nugget” emerged from the gravel. The nugget is the largest lump of gold ever discovered in the British Isles, weighing in at 682 grams. A model, cast at the time from the original, survives in the collections of the Natural History Museum in London. The Wicklow nugget itself was melted down: some say George III had it made into a snuff box.
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“In six weeks the miners recovered an incredible 80 kilograms of gold”
For the local prospectors, however, the Wicklow gold rush proved short-lived. On 15 October 1795, the Kildare militia seized the mine workings on behalf of the British government. Eighteen months later, an act of parliament legalised the takeover, which had been necessary, the government claimed, to “remove every temptation for the assembling of mobs, whose numbers had before that time increased to a very alarming degree”.
The authorities’ anxieties were well-founded. Just a year after that, the 1798 Rising – an early bid for Irish independence – halted the mining, as the workforce joined the rebellion. But the rising was quickly suppressed, and by 1800 the government’s mining operations were in full swing again. Scores of workers sieved the river sands and gravels for alluvial gold, washed into the river from some hidden source in the bedrock. Between 1795 and 1800, an estimated 300 kilograms of gold was retrieved by this method. Then, as returns from the river began to decline, an intense search began for the “mother lode” deep within the mountains – based on the popular notion that the gold usually lies in them there hills. “The mindset for gold-seeking prospectors, professional and amateur alike, has always been to think the gold must lie on the valley sides,” says geologist Norman Moles of the University of Brighton, UK.
The search for the mother lode was started by a young geologist called Thomas Weaver. On the slopes of Croghan Kinsella mountain, he ordered the digging of vast trenches in search of quartz veins rich in gold. Weaver’s trenches extended across almost 13 kilometres of hillside and are still visible in the landscape. Time and again the diggers struck quartz, but not a single vein yielded as much as a particle of gold. The geologists began to suspect that the alluvial gold did not have a local origin, and by 1803, the quest was abandoned. In the intervening years, commercial ventures have sporadically resumed the search, but to no avail.
Intrigued by this enduring mystery, Moles and fellow geologist Rob Chapman of the University of Leeds have adopted a new approach. First they spent weeks panning the watercourses in and around Gold Mines River, collecting more than 500 grains of gold from more than a dozen different localities – no fortune, alas, but enough to enable the researchers to determine the “microchemical signatures” of each site and then compare them. This powerful new technique takes advantage of the diverse character of naturally occurring gold. In nature, gold is always alloyed with other metals, particularly silver, in varying proportions. It often contains microscopic particles of other minerals that reveal what sort of mineral veins the gold originally formed in. By cutting and polishing sections of the panned gold grains and examining these sections under a scanning electron microscope, the geologists gathered clues to the bedrock source of the Wicklow gold.
Such microchemical techniques have already proved their worth. In a recent study Chapman and Moles worked with archaeologists to identify the likely provenance of the gold fashioned into spectacular torc necklaces during the Irish bronze age, between 3000 and 4000 years ago. The bronze-age goldsmiths turn out to have exploited indigenous gold from several sites far to the north of Wicklow, probably including Croagh Patrick in County Mayo, on the north-west coast of Ireland. By the iron age, however, nearly all the gold used by metalworkers was imported.
Now, the geologists have examined similar clues to the provenance of the alluvial gold that triggered the Wicklow gold rush. Focusing on this small region, they identified a variety of gold types, each with its own characteristic proportion of alloyed silver and with distinctive mineral inclusions. Their findings have ruled out two previous contenders for the source of the gold. One early theory maintained that the source was weathered gold-bearing copper ore near Avoca, and that glaciers or ancient run-off had carried the gold 8 kilometres south-west to Gold Mines River. But the signature of most of the gold from the river at the Red Hole is unique to the region, and is not found in gold from Avoca.
The second theory, akin to that proposed by Weaver two centuries earlier, is that the source lies nearer, in gold-enriched iron formations on Moneyteige Ridge, a kilometre to the west of the river. But again, the microchemical analysis tells a different story. Gold-bearing rocks from the ridge, analysed by two Irish geologists in the late 1980s, turn out to be incompatible with the microchemical signature of the Red Hole gold.
Chapman and Moles argue that the gold at the rich diggings of the Red Hole probably hasn’t travelled at all. Inclusions of “fool’s gold” – pyrite – are common in the gold here, indicating that this mineral was abundant at the site of the gold’s formation. In contact with air and water, pyrite decomposes to red iron oxides. Thus the Red Hole is probably a decomposed pyritic vein containing not just fool’s gold but real gold too. This theory explains why this place was by far the richest in gold: the weathered gold-bearing material would be easily eroded by the river to form a rich alluvial or “placer” deposit. It also explains why the Georgian prospectors found very little gold immediately upstream.
The geologists now reckon that, at some time in the distant past, a rich vein of pyrite and gold mineralisation was exposed and subjected to weathering. As an ancient river eroded this soft rock, a rich placer gold deposit formed. Then, during the last ice age, this old river channel, together with the decomposed gold vein, became capped with glacial deposits, burying the gold. The river channel subsequently shifted slightly to the west, yet the present river occasionally revealed the hidden treasure, as spied by the sharp-eyed schoolmaster. No one ever found the mother lode, because the gold in them there hills was in fact under the valley.
So is the Red Hole about to see the start of a new gold rush? Don’t bet on it. According to Chapman and Moles the much-sought gold source is likely to have been eroded away long ago, leaving only a tantalising residue trapped below the ancient course of Gold Mines River. It’s still possible that, somewhere in Wicklow, a rich deposit remains hidden below the mantle of glacial deposits. But it seems more likely that George III had the best of the Wicklow gold.
