by Phase and Feature
4.3.2 Worked stone
Rob Engl with a contribution by George R. Haggarty Introduction
A total of 43 finds of coarse and worked stone were recovered, six of which are part of a Purbeck limestone mortar. A catalogue of the illustrated material is included but a full report and catalogue of the coarse stone artefacts can be found in the site archive.
Raw material
The majority of the objects described below were formed from local granites. There were also smaller quantities of sandstone, mica schist, limestone, pumice and chalk cobbles.
Artefact categories by type Whetstones
The nine whetstones were all made of locally-obtained fine grained micaceous siltstones. Eight were hand-held and narrow with a rectangular cross-section. Four of the artefacts were fragmentary. Artefact SF3584 had a small ground hole, 9mm in diameter, at one end, probably for carrying cordage (Figure 4.34). A similar item, SF963, is well worn and has the remains of a heavily corroded iron chain for suspension surviving within a biconical perforation, bored at the widest end of the stone (Figure 4.34). Fragment SF1926 was probably originally part of a larger tabular object, though the rounded edges indicate it had continued to be used as a fragment.
Artefact SF3396 was flat and tabular.
Whetstones or hones were used throughout the medie-val period for the sharpening or edging of metal objects such as knives and razors (Ford 1987: 147).
Styluses
The assemblage contained four styluses, three of which were made of slate. The fourth, SF206, was made from mica schist. All of the artefacts are thin and cylindrical, ranging from 39mm to 67mm in length and from 2mm to 6mm in diameter. SF208 and SF3133 had single ends fashioned into a rough point while SF2700 and SF537 both had smooth flattened ends. Slate styluses, termed
‘pencils’, were found on both the St Nicholas and 45–75 Gallowgate sites, Aberdeen (Cameron et al, 2001: 207).
Spindle whorls
Three abraded spindle whorls were retrieved, all made of sedimentary rock. Two of these, SF2845 and SF3640, were bun-shaped while SF3849 was melon-shaped (Figure 4.35). SF2845 displayed a simple engraved line
SF3584
SF963 SF4281
SF3083
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Figure 4.34 Whetstones; SF4281; SF3083; SF3584; SF963
SF2845 SF2217
SF3849 SF3640
SF329 SF2583
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Figure 4.36 Grinding stones; SF2583; SF329
Figure 4.37 SF2583 as found, with handles and wedges in situ
decoration around the circumference while SF3640 appears to have cordage marks around its perimeter.
Grinding lathes
Two large circular stone artefacts are the grinding stones from composite grinding lathes. SF2583 survived virtually intact with the alder shaft in situ and secured tightly within the central hole of the grindstone by the use of oak wedges (Figure 4.36). Single wedges had been inserted down three faces of the shaft on either side of the grindstone and in two instances double wedges had been inserted (Figure 4.37 and see Section 4.2.1).
Heavily decayed wood was also found within the central pecked hole of SF329 suggesting that it was also part of a similar composite mechanism (Figure 4.36). This artefact has three, equally spaced, small depressions set
around a larger centrally placed hole. The outer faces of both stones show smoothed patches of wear with obvious striations.
It is likely that these artefacts represent the remains of foot-operated pole lathes for the edging or working of small metal objects such as knives, chisels etc.
The use of rotary grindstones in Scotland is evidenced from the Early Historic period – a rotary quern was recovered from 8th to 9th century contexts at Scatness, Shetland (Dockrill et al. 2010: 64), in a structure utilised as a storeroom or workshop. The example from Scatness was 224mm in diameter and 58mm wide (Bashford 2010: 242) and unlike the grindstones recovered from Aberdeen had a central square hole (50mm square) rather than a round one, having been manufactured from an old quernstone. An assemblage of 29 Anglo-Scandinavian cylindrical rotary grindstones, from 16–
22 Coppergate, York, ranged in size from between 50 to 440mm in external diameter, but were mainly under 100mm (Mainman and Rogers 2000: 2479). Two of the rotary grindstone fragments from York had external diameters of 240mm and 224mm, roughly comparable with the Bon Accord examples. Both had regular cone-shaped holes ground into one flat surface, similar to those on SF329, which may have been utilised in securing or rotating the stones (ibid: 2481).
Miscellaneous stone artefacts
Miscellaneous artefacts include a small bun-shaped
been used as an abrading tool in the smoothing of small wooden dowel rods.
Stone mortars George R. Haggarty (written 2015)
Recovered from the excavations were six badly abraded Purbeck limestone fragments (Figure 4.38), which almost certainly derive from a single large mortar with a 300mm interior diameter and 385mm exterior diameter. Two pieces were unstratified (SF6022 &
SF6023) and one each was recovered from fill (F) of Pit C019 (SF6024), fill (E) of Pit C069 (SF6025), Layer C010 (SF1656) and Layer C075 (SF6026), ranging from Phase 2 to Phase 5). A fragment of another mortar made of local sandstone was recovered from fill (E) of Pit C069, from Phase 3 or 4 (SF2393) while another small fragment from the rim of another sandstone vessel, perhaps a mortar, was recovered from fill (F) of the same feature (SF2207).
Purbeck marble is a hard, blueish-grey limestone composed predominantly of dark, fossilised shells from a small freshwater gastropod (viviparus cariniferus), set within a fine-grained matrix. Extensively exploited from the 12th century onwards as building material, the main period of mortar production appears to have occurred at quarries in the Isle of Purbeck, Dorset during the 13th and 14th centuries (Dunning 1977: 324).
A seaborne distribution has been noted (ibid), which explains their presence in a port such as Aberdeen.
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Figure 4.38 Purbeck Limestone mortar
from the substantial wear pattern on a large complete marble example recovered from a mid 20th century context in Portobello, that some may have had a long lifespan (Haggarty 2011: word file 25).
Previous excavation carried out at 45–75 Gallowgate, Aberdeen recovered a heavily abraded fragment from a small mortar, which was 160mm in diameter, thought most likely to be limestone and a product of Purbeck, from a layer of daub on the base of an oven dated to between 1375 and 1400 (Cameron and Stones 2001:
91, 207–08 illus 164 fig 495, 298–90). From the same excavation, a rim fragment from a stone vessel without a band, c. 210mm in diameter, was also recovered (ibid:
illus 25, fig 66), formed from a pure limestone (Trewin 1984: fiche 4: A4). Excavations carried out at 75 High Street, Perth recovered a heavy stone rim fragment, possibly a mortar, with an external rim diameter of 250mm, in what is thought to be Purbeck marble (A8450: C2476-3; Smith et al. 2011, 138). The authors also suggest that two other pieces of Purbeck marble were recovered from the site (A8221 & A5678).
Fragments of medieval Purbeck limestone mortars have also been recorded from a large number of sites in England ranging from Southampton (Platt and
Coleman-Smith 1975: 307–11) to York (Ottaway and Rogers 2002: 2799–802), but predominately in the south and East Anglia (Dunning 1977: 325).
Mortars made of Purbeck limestone seldom exceed 330mm in rim diameter, although a few larger examples have been recorded, with rim diameters of 391, 440 and 460mm. The largest, at 520mm, was found in the region of Hailsham (Parfitt 1976: 183). In the main they share certain features, including a broad rim band, four exterior nibs/lugs above four vertical projections/ribs.
These provided strength and enabled the mortar to be set into a wooden base. Surviving examples from the 18th century suggest this may have been a waist high log stood upright; this would have allowed the use of both hands in the grinding process. Mortars were used with a pestle for grinding various materials, including foodstuffs, and appear to have superseded rotary querns for grinding during the 13th century. Evidence from King’s Lynn suggests that they were in use from the 12th century, but only entered general use during the 13th and 14th centuries (Dunning, 1977: 327–29). This is in keeping with findings at Winchester which produced no mortars earlier than the mid 12th to mid 13th centuries, suggesting that mortars were introduced in the 13th century (Biddle and Smith 1990: 891). Recent
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SF2207
Figure 4.40 Possible mortar fragment; SF2207
SF2393 0 5cm
Figure 4.39 A Scottish mortar fragment; SF2393
work on the Southampton evidence shows that all the mortars were discarded within high medieval or later contexts. This and the high numbers of querns being discarded during the same phases and their absence from later phases suggests that querns were being replaced by mortars (Shaffrey internet report).
SF2393 was a thick stepped, concavo-convex stone mortar body sherd, broken on all its four edges and distinctively along a horizontal bedding plane on its upper side (Figure 4.39). It shows evidence of vertical cutting on its exterior below its rim band, and a smoothed dark grey stained interior, almost certainly due to grinding. It has an internal diameter of 220mm probably just below its rim and an exterior diameter of 330mm. The banding of the coarse-grained, light grey, sub rounded, quartz rich coarse sandstone is classed as a Sub arkose Quartz arenite, which has been well lithified possibly due to slight metamorphism (Simon Howard, pers comm). The grain size varies from 2mm to 18mm. There is an abundance of this material in the north-east of Scotland, so local manufacture seems a reasonable hypothesis. No Scottish parallels for this mortar are known. SF2207, a single sandstone rim sherd from a stone vessel, likely also represents a mortar (Figure 4.40).
Discussion
The worked stone assemblage represents both industrial and domestic activity from the prehistoric through to the post-medieval period. The working of textiles, perhaps in a domestic context, is represented by the recovery of spindle whorls, which are a common find on medieval sites. More developed industrial activity, including metalworking, was also evidenced.
The presence at Bon Accord of rotary grinding stones is likely representative of ferrous metalworking; these would have been utilised in finishing products and in sharpening tools. Similarly, the numerous hand-held whetstones could have been used in the finishing of edged tools. While the presence of the grinding stone, SF329, in a Phase 5 context accords with the evidence for ferrous metalworking in the late medieval/
early post-medieval period, the composite grinding mechanism SF2583 was recovered from the base of a Phase 1 pit, and indicates that metal tools were being used and perhaps produced on or near the site as early as the late 12th or early 13th century.
Other craft activities are represented by the presence of a pumice abrader, the fragments of a large Purbeck limestone mortar, and what are likely to be a locally produced sandstone mortars. The pumice was possibly associated with the processing of hides. The relatively
context. It may have been used in the grinding of material to be used as a tanning or dyeing agent. This use has been suggested for the fragmentary limestone mortar recovered from 45–75 Gallowgate. Pollen analysis on the interior of the Gallowgate mortar indicated the presence of oak, Scots pine, birch, alder, willow, hazel and elder, along with residues of tormentil and dock, both of which were utilised in the tanning and dyeing processes (Moffat and Penny 2001: 298–99).
The provenance of this mortar, from the south-west of England, illuminates the extent of trade between Aberdeen and distant parts of the British Isles.
Catalogue of illustrated worked stone items (L = length; W = width; Th = thickness; D = diameter)
SF 963 (Figure 4.34) Phase/Feature Phase 2/Layer C014
Description: whetstone with metal attachment Tapering rectangular micaceous siltstone whetstone with squared ends, perforated at widest end with small circular hole (D c. 6mm) to facilitate suspension, probably from a belt. Two links from a fine figure-of-eight link chain are threaded through perforation, visible on x-ray. Corrosion from iron chain has caused cracks to form at one corner of the stone. L 92.5mm; W 5.5–17mm; Th 5–8mm
SF 3584 (Figure 4.34) Phase/Feature Phase 3 or 4/Pit C048 Description: whetstone
Siltstone. L 127mm; W 28mm; Th 15mm. Narrow rectangular whetstone. Very worn with one face having a small depression. Small ground hole (9mm x 9mm) for carrying cordage placed at one end.
SF 4281 (Figure 4.34) Phase/Feature Phase 1/Gully C001 Description: whetstone
Siltstone. L 81mm; W 50mm; Th 35mm. Roughly triangular fragment of whetstone. Rectangular in section. Worn depressions on two larger faces. End missing.
SF 3083 (Figure 4.34) Phase/Feature Phase 2/Pit C022 fill (A) Description: whetstone
Siltstone. L 35mm; W 9.5mm; Th 9.5mm. Fragment,
‘door wedge’ shape and rectangular in cross-section.
SF 2845 (Figure 4.35) Phase/Feature Phase 2/Pit C022 Description: spindle whorl
Sedimentary rock. L 34mm; W 34mm; Th 10mm.
Circular, flat, bun-shaped loom weight with centrally
SF 3640 (Figure 4.35) Phase/Feature Phase 5/Layer C009 Description: spindle whorl
Spindle whorl. Sedimentary rock. L 24mm; W 23mm; Th 7mm. Abraded, bun-shaped spindle whorl with cordage marks around the perimeter.
SF 3849 (Figure 4.35)
Phase/Feature Phase 6/Spread A043, between Layers A008 and A009
Description: spindle whorl
Sedimentary rock. L 33mm; W 20mm. Abraded, melon-shaped spindle whorl.
SF 2217 (Figure 4.35) Phase/Feature Late Phase 4/Layer A004 Description: worked stone disc/potlid
Granite. L 55mm; W 51mm; Th 9mm. Roughly fashioned tabular disc of granite with flaked edges. Possible potlid.
SF 329 (Figure 4.36) Phase/Feature Phase 5/Pit C080 Description: grinding stone
Granite. Circular stone, 170mm in diameter and 75mm thick, of which roughly half survives. A large central pecked hole, 52mm in diameter pierces the stone.
One face has three equally spaced ground circular depressions, one of which has been partially removed by damage. These depressions are 22mm x 12mm (depth).
The outer edge of the artefact appears intentionally pitted with large patches of very smooth wear >30%.
SF 2583 (Figures 4.36 & 4.37) Phase/Feature Phase 1/Pit C001
Description: grinding stone
This is an element of a composite wood and stone grinding mechanism, the wooden component of which is described in Section 4.2.1 (SF2583). The grindstone is made of a mica-rich, fine-grained sandstone. It is 230mm in diameter and 93mm thick. The shaft hole, which is roughly 90mm in diameter, is positioned slightly off centre and has been crudely fashioned through pecking. The outer surface of the grindstone has been worn down and is now concave in profile.
Numerous faint yet distinct striations are also present over the entire working face of the grindstone.
SF 1656, 6022, 6023, 6024, 6025 & 6026 (Figure 4.38)
Phase/Feature Phases 2 to 5/Pit C019, Pit C069, Layer C010, Layer C075 and unstratified Description: mortar
Purbeck limestone. Internal D 300mm; external D 385mm; surviving H 205mm. Large mortar.
SF 2207 (Figure 4.40) Phase/Feature Phase 3 or 4/Pit C069 Description: mortar
Sandstone. Internal D 255mm; external D 350mm;
surviving H 40mm. Rim of possible mortar.
SF 2393 (Figure 4.39) Phase/Feature Phase 3 or 4/Pit C069 Description: mortar
Sandstone. Internal D 220mm; external D 330mm;
surviving H 60mm. Rim of possible mortar.
4.3.3 Lithics Rob Engl Introduction
A total of 247 pieces of chipped stone were recovered from Bon Accord. A catalogue of the secondarily modified artefacts (including illustrated material) is provided but the complete report can be found in the site archive.
Raw material
The assemblage appears to be of mixed origin. Flint accounts for 238 of the 247 pieces recovered with the remainder consisting of chert (n.4), quartz (n.2), agate (n.2) and a single flake of fossilised wood.
The flint has a broad colour range with colours typical of assemblages from Aberdeenshire dominating. Honey coloured flint (n.118) is most common followed by pale grey (n.71) and red (n.16), colours typical of material derived from local Buchan gravel deposits. Other more widespread sources of flint are also represented in the assemblage. Nine pieces showed a dark blue/black colour occasionally combined with a chalky cortex.
This may indicate primary source chalk flint imported from the south-east of England as ‘ballast’ flint in post-medieval and modern times. However, such material may also have been washed ashore from submerged deposits in the North Sea. A further 11 pieces are a mottled dark grey or brown (including a sidescraper SF4263B and platform core SF3706). This may represent material imported from the Yorkshire Wolds during the Neolithic and Early Bronze Age. The variety of raw material derivations present within Aberdonian assemblages has been previously alluded to by Saville (2001: 259) in his discussions of the lithic assemblages recovered from Castle Street and 16–18 Netherkirkgate.
The assemblage is relatively fresh in appearance with 69% of the flint showing little or no signs of patination or burning. Burnt or heat-treated material accounts for only 10% and patinated material 19%.With the exception of the chalky material mentioned above, the cortex has a largely rolled and water-worn appearance suggesting that it was obtained from the nearby shoreline or rivers. The other supplementary materials were also probably derived from these sources.
Primary technology
Debitage dominated the assemblage and most major classes were represented. Flakes (n. 117) were most numerous, with the majority being regular and often bladelike in character. True blades (W > 8mm – n.23) and bladelets (W < 8mm – n.1) were fewer in number but were again very regular and parallel sided. Only two of the blades were fragmentary and this was probably caused by post-depositional factors given that this area has undergone extensive activity.
The presence of simple, crushed and facetted striking platforms suggest that both hard and soft hammer reduction techniques were being practised.
The presence of 30 cores within the assemblage alongside tested and intact nodules, waste debris such as chips, fragments and chunks and modified tool types suggests that material was being directly worked on-site.
Of the 30 cores recovered during the excavation, all but three were made on flint. Bipolar (n.13) and platform cores (n.12) are the most common and there are also four amorphous examples and a core fragment. The platform cores are relatively small examples with a mix of narrow blade and blade-like flake removals. Eight of the examples were single platform types worked up to 50% of the striking platform surface. Two have opposed platforms and two have multiple examples. The presence of these cores would suggest a Late Mesolithic occupation of the site. However, no other strongly diagnostic tool types of this period have been found within the assemblage. It is likely that these platform cores relate to an early Neolithic occupation with their form being dictated by the relatively limited size of the parent material.
The presence of bipolar and amorphous cores indicates that an expedient lithic technology was practised on-site alongside the more formal platform struck technique. Many of the bipolar cores had been worked down to a fairly small size. This technique is often associated with the working of small, intractable pebble material (Engl 2008: 231). However, at Bon Accord only two flakes showed recognisably bipolar characteristics such as crushed platforms and associated opposing flake scars. This mirrors the findings at Kintore (ibid:
231) where a similar assemblage composition suggested that the bipolar technique had been introduced either to extend the flake producing life of the platform cores or to work very small or intractable material.
Secondary technology
scrapers, a notched blade and flake, a retouched blade, a leaf shaped arrowhead and an abrading tool. A catalogue of the material is given below.
Catalogue of lithics
(L = length; W = width; Th = thickness; D = diameter) SF 4320 (not illustrated)
Phase/Feature Phase 1/Gully C001 Description: abrading tool
Honey flint. L 44.8mm; W 13mm; Th 7.5mm. Blade-like flake with heavy utilisation scars along left lateral edge.
The right lateral edge has very fine retouch along its length probably to aid handling during use.
SF 4263B (not illustrated) Phase/Feature Phase 5/Layer C009 Description: sidescraper
Honey flint L 31.6mm; W 17.3mm; Th 4.4mm.
Sidescraper made on primary flake. Abrupt fine regular retouch along left lateral edge.
0 5cm
SF2085a
SF2285a SF3014 SF4408
Figure 4.41 Lithics; SF4408; SF2085A; SF3014; SF2285A