1993:096 - LAMBAY ISLAND, Dublin

In September/October a small-scale excavation was carried out over a two-week period on Lambay. The purpose of the excavation was to see if there was evidence of the working of porphyritic andesite (porphyry) for stone axe production. The excavation formed part of the broad research strategy of the Irish Stone Axe Project. The site is in a valley running north-west to south-east, close to the western edge of the eastern upland area of Lambay, with a fine view and access to the lower lying western part. The sides of the valley are formed by outcrops of porphyry which have small dished areas, potentially the result of quarrying. Two cuttings (each 4m x 2.5m) were opened, one on each side of the valley where fieldwork had shown that there were struck flint flakes visible in a deposit of porphyry pieces below the outcrop. In the north-facing cutting (Cutting 2) a leaf-shaped arrowhead of flint (and a chip of struck flint) was found stratified in a dense mass of small porphyry pieces sitting over a shelf in the bedrock. This covered bedrock surface had indications of being worked in the form of indentations on the face and in the presence of a large detached block of porphyry. To the north of the outcrop however it was clear that modern activity had extensively disturbed the area. Here there were some struck flint flakes and modern pottery at the same stratigraphic level and either a cultivation furrow or a narrow ditch with the blade of an iron shovel in situ.

In the south-facing cutting (Cutting 1) further to the south-east there was less sign of modern disturbance and here again a mass of porphyry pieces overlay bedrock and spread out beyond it. There was definite layering in this deposit; below a zone of angular pieces there was more varied material, pieces of porphyry from pea size upwards, both rounded and angular. This overlies a dense mass of stone which includes a setting of sandstone slabs defining a rectangular area up to 1m in length. There were a few hundred flint flakes found in this small cutting, struck from cores which were beach pebbles brought up to the site from the coast and a number of hammerstones used to strike the flint. The diagnostic artefacts, such as a concave or hollow scraper, indicate a Neolithic date for this material. The flint was found from the top to the base of the deposit of porphyry pieces. Associated with the apparent working of the porphyry are a small number of potential roughouts for axe heads, one with signs of pecking, and some pieces of sandstone showing wear which may have been used to ground down the surface of porphyry after it had been hammered and pecked. At the south end of the cutting a stone (sandstone) adze head was found but probably in a disturbed context.

What is of particular significance about this evidence is that up to now our knowledge of axe production in Ireland has been centred on those rocks, like the porcellanite found at Tievebulliagh and Brockley on Rathlin Island, which can be flaked into rough shape and this process leaves distinctive waste flakes. The primary method of working porphyry would have been by hammering and pecking and the by-products of this kind of production have been notoriously hard to find. It would appear at the moment that what we have found on Lambay is the first example of this kind of axe production site in Ireland. It is hoped to continue work on the site in 1994.

For context of the excavation, see Cooney, G. 1993. 'Lambay: an island on the horizon', Archaeology Ireland 26, 24–8.