"Rock of the Month # 223, posted for January 2020" ---

We start 2020 with a striking exhibit from Ireland. The Irish content is long overdue, and this is the first of three months'-worth of features from the Emerald Isle. Whereas the majority of stone tools studied by archaeologists are for utilitarian, day-to-day usage, such as knives, scrapers and projectile points, artistic creations such as beads are locally important. This month's example is especially noteworthy, an early example of a tool specific to the production of gold jewellery.

The National Museum of Ireland: Archaeology, beside Merrion Square, in the elegant Georgian core of Dublin just south of the Liffey river, houses antiquities from 7,000 B.C. to the late Medieval period and beyond. It was founded under an Act of 1877. A highlight of the public displays is an exhibit of the use of gold in ornaments and jewellery (Kelly, 2007, pp.15-21). The display of gold and bronze objects (as seen in 2019) is very impressive. The exhibits include:

• Some of the older examples include a lunula from (?) county Sligo, 2000-1800 B.C., and one from Galway, circa 2000 B.C. Other lunulae of this period were found across counties Donegal, Monaghan and Kilkenny.
• A bronze anvil that fits in the palm, circa 1200 B.C. This piece is from the Bishopsland hoard in county Kildare, with late Bronze Age goldsmithing tools. Tin is also used, as in tin torcs from Kilsallagh in county Longford, circa 1200-1100 B.C.
• The use of Au in ornaments and jewellery - around 1200 B.C. there was a change in style, with many items like torcs made by twisting square bar (strips with square cross-section), suggesting that a major gold discovery had been made around that time. Examples of gold torcs come from counties Westmeath, Roscommon, Meath, Mayo, Galway, Kildare and Antrim, all circa 1200-1000 B.C.
• A central area in the gold display has large items, such as big gold collars as from Gleninsheen, county Clare, 800-700 B.C., and another from Ardcrony, county Tipperary, 800-700 B.C. An interesting example of same period shows lines of raised, punched domes, county Clare. The great Mooghaun gold hoard was found in March 1854 by workers building a railway between Limerick and Ennis. The site is Mooghaun North, county Clare, circa 800-700 B.C.). Collars, neck rings and many bracelets were recovered, most of them unfortunately melted down, but 35 of 146 pieces in an early display survive, 21 in the Irish Museum and 14 in the British Museum. Limavady (in Ulster, the northeastern of the four old provinces if Ireland) was the site of another gold hoard ploughed up by a farmworker, leading to the Gold Ornaments Trial of 1893, which saw the hoard restored to Ireland (the case was significant in terms of the legal treatment of treasure trove: Praeger, 1937, pp.63-67).
• In the late Bronze Age, 1000-500 B.C., many items were made from gold sheet, such as an ornamented disc from county Armagh, circa 800-700 B.C. Also shown are gold-covered sunflower pins from Ballylegan, county Laois, circa 800-700 B.C.

Figs. 2-3: Stone tools, including the stamp of Figure 1, and an example of ancient Irish goldsmith work. The latter, item 1990:71, is from county Galway, circa 2000 B.C. Specimens on display at the Irish National Museum of Archaeology, in downtown Dublin, photographed in September 2019.

The artefacts on display in Dublin have analogues in Scotland, as shown by Alison Sheridan (in Clark, 2014, pp.39-59). Lunulae are known in both countries, back to circa 2000 B.C., and one example shown by Sheridan is from Blessington, county Wicklow (ibid., p.41), on the west side of the Wicklow Mountains south of Dublin.

Ireland has a long mining history. Bronze Age copper mining in Cork and Kerry counties involved at least 74 mines of proven or probable early Bronze Age date (Craddock, 1980). 73 are of "Mount Gabriel type", exploiting syngenetic copper deposits in the Devonian Old Red Sandstone, at an average grade of 0.5% Cu, while the other deposit, at Derrycarhoon, exploited a larger, vein-type deposit. However, whereas Ireland had abundant copper and gold in the Wicklow and Kerry hills, tin (for converting copper to tougher bronze) required trade with Cornwall. Flat axes and gold insignia (lunulae) were traded for black cassiterite pebbles (Fox, 1964). Southwestern English and Irish Cu cannot be distinguished with certainty, since both have a high arsenic content (ibid., p.82).

Gold deposits of Ireland

Rocks of Caledonian age are the main host of known Au deposits in Ireland. Principal settings for gold in Ireland (McArdle, 1989; see also Steed and Morris, 1986; Simpson et al., 1989; Thompson et al., 1992; Wilkinson, 1996; Smyth, 2004; Lusty et al., 2011) include: (1) the Avoca area, in volcanogenic massive sulphides, quartz veining and banded iron formation; (2) quartz veins and lower Paleozoic wallrocks in south Mayo; (3) stibnite- arsenopyrite veins of Clontibret in the Longford-Down inlier; and (4) Au associated with sulphide deposits in the Dalradian of west Ireland, as in Connemara (see e.g., Parnell et al., 2000). The Curraghinalt gold deposit in N.Ireland is a high-grade Au deposit, with the metal hosted by at least ten quartz-carbonate veins. At one point (Anon, 2013) the estimated endowment included measured resources of 0.02 MT grading 21.51 ppm Au, indicated resources of 1.11 MT grading 12.84 ppm Au and inferred resources of 5.45 MT grading 12.74 ppm Au. Curraghinalt, at an aggregate resource of 2.77 million ounces, is the largest-known Au deposit in the Sperrin Mountains of Northern Ireland. The gold mineralization in the quartz-sulphide veins in Dalradian metasediments has been dated to the Grampian event of the Caledonian orogeny, between 462.7 and 452.8 Ma (Rice et al., 2016).

Provenance studies

The next consideration, having determined the use of the tools, and surveyed the local geology, is the source of the metal itself, which may be either near or far (or both). Gold metal tends to contain impurities, most often silver, but also copper, iron and other elements. Provenance can be constrained by analyses of gold in both ore and artefacts. One finding is the recognition of gold recycling by the remelting of artefacts (Cahill et al., 1997). As noted in the previous section, there was ample gold found in Ireland in ancient times, probably mostly in stream gravels (placer gold) where the metal would be concentrated in heavy-mineral sands, having been released from its bedrock sources by weathering. A short compilation of analyses of gold articles in a survey of ancient county Fermanagh (southwestern Northern Ireland) indicates Au as the main component, followed by Ag. Trace to minor Cu and Sn were also present (McHugh and Scott, 2014, p.105).

References

Anon (2013) Dalradian seeks to optimize Curraghinalt. Northern Miner 99 no.39, 23, 11 November.

Cahill,M, Chapman,RJ, Leake,RC, Shell,CA, Taylor,JJ, Warner,RB and Watling,RJ (1997) Identification of the exploitable gold ores of Britain and Ireland and their relation to early prehistoric gold artefacts: recent advances with LA-ICP-MS analysis. Metals in Antiquity conference, Harvard University, Abstracts volume, p.17.

Clark,NDL (2014) Scottish Gold: Fruit of the Nation. Neil Wilson Publishing Limited / The Hunterian, University of Glasgow, 112pp.

Craddock,PT (editor) (1980) Scientific Studies in Early Mining and Extractive Metallurgy. British Museum Occasional Paper No.20, 175pp.

Fox,A (1964) South West England. Ancient People and Places 41, Thames and Hudson, London, 254pp.

Kelly,EP (2007) Guide to the National Museum of Ireland: Archaeology. National Museum of Ireland, Dublin, 48pp.

Lusty,PA, Naden,J, Bouch,JJ, McKervey,JA and McFarlane,JA (2011) Atypical gold mineralization in an orogenic setting - the Bohaun deposit, western Irish Caledonides. Econ.Geol. 106, 359-380.

McArdle,P (1989) Geologic setting of gold mineralization in the Republic of Ireland. TIMM B98, 7-12.

McHugh,R and Scott,BG (2014) The prehistoric period: the prehistoric archaeology of County Fermanagh. In "An Archaeological Survey of County Fermanagh", Volume 1, Part 1 (Foley,C and McHugh,R editors), Northern Ireland Environment and Heritage Service / Colourprint Books, pp.55-138,953-987.

Parnell,J, Earls,G, Wilkinson,JJ, Hutton,DHW, Boyce,AJ, Fallick,AE, Ellam,RM, Gleeson,SA, Moles,NR, Carey,PF and Legg,I (2000) Regional fluid flow and gold mineralization in the Dalradian of the Sperrin Mountains, Northern Ireland. Econ.Geol. 95, 1389-1416.

Praeger,RL (1937) The Way that I Went. Collins Press Ireland, 2nd edition, xii+394pp., republished 2014.

Rice,CM, Mark,DF, Selby,D, Neilson,JE and Davidheiser-Kroll,B (2016) Age and geologic setting of quartz-vein-hosted gold mineralization at Curraghinalt, Northern Ireland: implications for genesis and classification. Econ.Geol. 111, 127-150.

Simpson,PR, Gallagher,MJ, Green,PM, Middleton,RS, Raiswell,R and Williams,RAC (1989) Gold mineralization in relation to the evolution of extensional volcano-sedimentary basins in the Scottish Dalradian and Abitibi belt, Canada. TIMM B98, 102-117.

Smyth,D (2004) Orientation biogeochemical prospecting studies in Ireland. Geochemistry: Exploration, Environment, Analysis 4, 87-95.

Steed,GM and Morris,JH (1986) Gold mineralization in Ordovician greywackes at Clontibret, Ireland. In `Turbidite-Hosted Gold Deposits' (Keppie,JD, Boyle,RW and Haynes,SJ editors), GAC Spec.Publ. 32, 186pp., 67-86.

Thompson,SJ, Shine,CH, Cooper,C, Halls,C and Zhao,R (1992) Shear-hosted gold mineralization in Co. Mayo, Ireland. In `The Irish Minerals Industry, 1980-1990' (Bowden,AA, Earls,G, O'Connor,PG and Pyne,JF editors), Irish Association for Economic Geology, Dublin, 436pp., 21-37.

Wilkinson,JJ (1996) Faulting, fluid pressure fluctuations and gold mineralisation at the Croagh Patrick quartz-gold vein deposit, county Mayo, Ireland. GSA Abs.w.Progs. 28 no.7, 152, Denver.