bedrocks and bullauns
DESCRIPTION
A re-assessment of the function of Irish bullaun stonesTRANSCRIPT
BEDROCKS ANDBULLAUNS: more thanone use for a morta r?Brian Dolan wonders whether complacency has affected the
interoretat ion of bul launs.
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lntroductionBullaun stones are one of those classic Irish
archaeological monuments that everyoneknows about, many have seen, but few have
really thought about in any serious way,
largely because of their seemingly enigmatic
function. They are basically scoops or
hollows in large stones, tlpically lacking
any fill or context that might betray their
functions.My interest in the role-or multiple
roles-of bullauns in the past was piqued
when reading a recent article in ArchaeologyIreland (Autumn 2008) by Matt Kelleher and
Caimin O'Brien which discussed some stone
basins, cut into bedrock underlying peat in
Meelaghan, Co. Offaly, that look very
similar to stone mortars used for grindinggrain in a number of Native American
cultures. The authors suggested that these
features do not fit into the traditional
understanding of bullauns as 'a single
depression found in association with an
ecclesiastical site' and should be classifiedseparately as 'bedrock mortars', implying a
use in food production.What struck me, howevet, was how
similar these stones also are to mortars forgrinding iron ores that I have seen in the
archaeological literature. The idea of
bullaun stones being used for the crushingof metallic ores is not new but it has beenoverlooked by Irish archaeologists in favourof interpretations focusing on theprocessing of grains, nuts and seeds or on
religious/ritual explanations. Further
research made clear that associations with
early metalworking may be significant for atleast a subset of bullaun stones and, moreimportantly, that this could be testedthrough both excavation and survey.
Previous researchThe seemingly intractable nature of bullaunstones has meant that few have thought to
study them, let alone define orsystematically analyse them. Hypothesesregarding their function have changed little
since they were first identified in the late
nineteenth century, and the last maior
article on the topic, published by Liam Price
exactly 50 years ago, still awaits an update(although significant work has been carriedout recentlyby David McGuinness as part ofa doctoral project in UCD). There is ageneral acceptance, based on their
Archaeology lreland Spring 2009
Opposite page: Bullaun stone fromGlendalough, Co. Wicklow (photo: TerryO'Hagan).
Right: Conical ore-crushing hollows fromMugharet al Warda, Jordan (photo: Yosha Al-Amri).
consistent association with earlyecclesiastical sites, that the stones date fromthe early medieval period, but problems ofdefinition, classification and dating stillremain.
Possibly the most crucial issue in thestudy of bullaun stones has been theunverifiable nature of the most populartheories about their use. This is due to a lackof relevant historical sources and theephemeral nature of many of the activitiesthat have been associated with them. Owingto this lack of evidence, interpretations ofbullaun stones have relied heavily onfolklore as well as ethnographic andhistorical analogy.
The use of 'knocking stones' in Scotlandand Ulster in the early modern period forpounding barley and oats, combined withethnographic and historical examples ofsimilar stone-cut basins from across theworld being used for food production, haveprovided the best argument for bullaunstones having a similar use in lreland.
Peter Harbison has convincingly linkedsome bullaun stones in the Dingle Peninsulawith pilgdmage as part of a package ofremains associated with early pilgrim routes.The association of many bullaun stoneswith ecclesiastical sites certainly appears topoint to some form of religious context fortheir use, but evidence of metalworking onmany church sites, such as Clonfad, Co.Westmeath, or Clonmacnoise, Co. Offaly,may point to an underlying industrial causefor the association. This might also explainthe occurrence of bullauns in isolatedlocations and in association with secularsites. Other interpretations of the bullaunsas cursing stones, as having curativeassociations or as baptismal fonts have beenbased on a mixture of conjecture andfolklore. Little or no direct evidence for theiruse, or indeed their date, has been found,and this has forced a reliance on analogyand speculation.
Archaeology lreland Spring 2009
Bullauns and metallurgyVery little is knorrm about the extraction orprocessing of metallic ores in early medievalIreland. It is clear, both from thearchaeological evidence and the texts, that avariety of metals, particularly iron andcopper, were mined, processed and smeltedon a fairly regular basis. No mines from theperiod have been identified archaeologicallybut they are mentioned in the law-tracts.Ore, once extracted, is usually processed, i.e.broken up into smaller pieces, sorted and,depending on the ore, roasted prior tosmelting. A verse in tl:te Dindsenchas of AillnCobthaig specifically mentions the crushingof ore by the Sil mBuinne of Bantry after itwas quarried; unfortunately it is not clearwhether this took place at the site ofextraction or elsewhere.
The crushing and sorting of ore, termedbeneficiation, is necessary in almost all casesprior to smelting. Methods of crushing varyfrom the use of simple stone hammers tothe rolling of hear,y boulders over ore spreadon a flat rock. Two methods known fromIndia result in stone basins or depressionsvery similar to those classified as bullaunstones in lreland. Crushing ore on flatboulders or rock outcrops using hand-heldhammers or pestles produces a shallowdepression which, upon reaching a depth ofc. 10cm, begins to abrade fingertips as wellas ore, resulting in stones with multiple
B U L L A U N S
depressions on their surface. Anothermethod, used in Rajasthan, involves thecreation of large mortars, c. 5Ocm indiameter and 50cm deep, for the crushing ofsilver-lead ores with large iron or iron-shodpestles. Similar mortars, in an outcrop ofbedrock associated with a Byzantine ormedieval iron-mine, have recently beenidentified in Jordan.
Normally, beneficiation is carried out inor close to a mine or extraction site,although in the case of bog ore waterloggedconditions may have necessitatedprocessing elsewhere. The smelting site,which could sometimes have been adjacentto the ore source, may have seen furthergrinding of ore, depending on the metalbeing extracted and the smelting techniqueused. Smelting sites are also often locatedclose to sources of fuel, population centresor in socially prescribed areas.
Superficially at least, an obviousanalogy can be dranrn between Irish bullaunstones and the ore-crushing mortarsdiscussed, but, crucially, there is alsoarchaeological evidence to support thecomparison. Some of the most convincingevidence comes from Gallen Priory, whereKendrick found an ironworking area withdeep pits of iron slag and burnt earth and ahuge stone slab over 2mIong. The slab hada 'basin' 50cm in diameter 'scooped' out ofit, which the excavator presumed was for
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which was interpreted as a potential bullaun
owing to an artificial depression on its
surface. Cut into the fill of the pit was a
possible furnace or hearth bottom lined
with a dense layer of charcoal and slag.
Less direct evidence for the association
of stone mortars with metalworking comes
from the hut site of Glannafeen, Co. Cork,
likely to date from the Iron Age or the early
medieval period. A spur of bedrock running
through the hut, which contained a stone-
lined iron-smelting furnace, had a circular
bullaun-like hollow shown on the plan but
not discussed in the text. At Drumnakill, Co.
Antrim, an early church site, E. E. Evans
noted a large bullaun cut into a flat dolerite
block and surrounded by large amounts of
iron slag. More circumstantial evidence
comes from sites like St Gobnet's House,
Balllwourney, or Clonmacnoise, Co. Offaly,
where both metalworking and bullaun
stones are recorded but with no direct
associations.
Testing the theoryThe evidence outlined above is very
suggestive but not conclusive. The obvious
next step is to identify a representative
group of bullaun stones in a landscape for a
systematic suwey, involving geophysics and
test-pit excavation. The group at
Glendalough, Co. Wicklow, Iocated in a
mineral-rich area, is an obvious candidate.
For example, a magnetometry suwey carried
out in the vicinity of the bullauns, but also
critically further away as a control, could
Archaeology lreland Spring 2009
detect the remains of smelting operations:
ores, roasting pits, slag, hearths and
furnaces. This could be followed up by
excavation to investigate the character of
any anomalies. Further studies could extend
the scope of such investigations to other
sites, such as those not associated with
ecclesiastical or monastic complexes.
If there is a spatial link between bullaun
stones and extraction sites then these stones
may provide signposts for locating
previously unknown mines-and, in the
case of bog ore deposits, long-destroyed
bogs. This would be particularly true of
bullauns in primary locations, such as the'bedrock mortars' proposed by Kelleher and
O'Brien.
Conclusion
Bullaun stones have been known and
researched since the nineteenth century and
it is perhaps this long history that has led to
complacency in their study. In reality, the
term 'bullaun', as used by Irish
archaeologists, is a generic one,
incorporating any hemispherical hollow in
a large stone not demonstrably prehistoric
or natural. It is very likely that the various
depressions we characterise as bullauns
include monuments that do not share a
single chronology or function.
It is hoped that this article has offered
not only a potential use for some bullauns
but also some plausible evidence and a
direction for future study. Further work on
the classification and definition of bullauns
Above left: Possible bullaun stone from theCarrick, Loch Lomond, Scotland (photo
courtesy of David Sneddon).
Above: Ore-crushing mortar fromBofeenaun, Co. Mayo.
and sub-types such as bedrock mortars, as
well as characterisation according to their
location, may provide new insights into
their place in early medieval society and
economy. There is clearly potential to
progress from arguments relying on
folklore, analogy and conjecture to
explanations based on archaeological
real i t ies and methodologies.
AcknowledgementsThanks to Dr Aidan O'Sullivan and Maureen
Doyle for advice and comments on previous
drafts. Thanks also to David Sneddon, TErry
O'Hagan, Conor McDermott and Dr Yosha
Al-Amri for providing images. Finally,
thanks to the IRCHSS and the National
University of Ireland for funding my Ph.D
research. I
ReferencesCraddock, P.T. 1995 Early metal mining and
production. Edinburgh University Press.Kendrick, T.D. 1939 Gallen Priory
excavations, 1934-5. loumal ofthe RoyalSociety of Antiquaries of lreland 69, I-20.
Price, L. 1959 Rock-basins, or'bullauns', atGlendalough and elsewhere. loumal ofthe Royal Society of Antiquaries of Ireland89, 161-88.
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