4.1 Results: blank controls

The raw material used to produce the experimental flakes was examined microscopically to observe any natural irregularities that might be mistaken for residues. It was found that the Wolds flint contained crystal inclusions of two types: 1) irregular white to brown angular crystals (Figure 15), and 2) rectangular linearly arranged crystals (Figure 16). These crystalline materials might be misinterpreted as bone or antler, highlighting the need to study raw stone materials and their natural irregularities prior to analysis of archaeological stone tools.

Figure 15
Figure 15: Non-residue within blank control – irregular white to brown angular crystal inclusions in flint
Figure 16
Figure 16: Non-residue within blank control – rectangular linearly arranged crystals in flint

After 11 months, heavy crystal formation on the soil surface of the wetland unit 2 was visible macroscopically (Figure 16), and microscopic examination of flakes from this unit shows that authigenic microcrystals also grew on all flakes, including the blank control (Figure 17). These crystals were not removed by the usual cleaning process with a stream of ultrapure water. These microcrystals are possibly a form of gypsum (CaSO4.2H2O), based on the rosette and lath-shaped growth habit observed, that is identical in appearance to gypsum (Shih et al. 2005, 257). Crystal formation was so heavy under and around fish-scale residues on the flake buried in the wetland for 11 months, it was visible macroscopically as a white powdery material (Figure 18); microscopically, the individual crystals were distinguishable (Figure 19).

Figure 17
Figure 17: Crystal formation in the soil in unit 2 wetland at Star Carr, after all experimentally used flakes were removed after 11 months. Fine crystals were also found on the blank flake and all residue-containing flakes from this unit
Figure 18
Figure 18: Blank control flake buried in the wetland exhibiting some authigenic crystal growth after 1 month
Figure 19
Figure 19: Flake with fish-scale residues, after burial for 11 months in the wetland unit. Note white powdery crystal formation around and underneath scales
Figure 20
Figure 20: Micrograph showing crystal formations under fish scale after burial for 11 months in wetland unit 2

Changes to blank flakes resulting from burial condition were documented. Soil residues from the burial environment were found on all six controls from all units and burial intervals. Such soil residues could hypothetically be mistaken as potential anthropogenic residues. In particular, the soil residues seen adhering to the control flakes buried in the dry land for both 1 month and 11 months were concentrated along one edge in a way that might be misinterpreted as a residue from tool use. The blank flake buried in the alkaline unit 3 for 1 month showed a green growth on the flint surface (Figure 21). This could be a chlorophyll-containing lichen, although hyphae comprising the fungal symbiont were not immediately apparent under the microscope.

Figure 21
Figure 21: Blank flint buried in alkaline unit 3 for 1 month showing green growth on surface, possibly lichen

All blank control flakes buried alongside the residue-containing flakes in each burial set were found to have no residues. This means no residue transfer occurred owing to horizontal movement of residues from experimental pieces to the controls during burial.


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