1	Is it Real or is it a Reproduction? A 3-Step Process for Evaluating the Authenticity of Siliceous Artifacts – Flint / Chert Presented by Jim Fisher B.A. M.Ed.
2	STEP 1 - REVIEW CHEMICALLY INDUCED PROPERTIES Inspect surface for evidence of alteration due to natural chemical weathering Utilize microscopic review of weathering phenomena as a potential dating method
3	Understand the nature of chert: Chert forms through chemical precipitation Nodular and bedded forms often occur in carbonates Chert can be microscopically fibrous or microcrystalline (cryptocrystalline) Chalcedony– chalcedonic (fibrous) microstructure Members of the silica family silicates – siliceous – SiO2
4	Compare naturally weathered and “fresh” lithic samples Visible and invisible chemical differences exist between surfaces of “fresh” source samples of chert and archaeological artifacts made from the same material. Weathering can oxidize or reduce minerals on the surface of an artifact.
5	Compare naturally weathered and “fresh” lithic samples (cont.) Groundwater may dissolve some elements and then deposit others in resulting pores (mineral dissolution and replacement).
6	Carbonate mineral dissolution and replacement at 20X magnification
7	Inspect for effect on mineral inclusions / impurities Some are unstable at surface conditions Surface implies exposure to elements exterior to the parent material resulting in post-depositional modification
8	Inspect for effect on mineral inclusions / impurities (cont.) Clay minerals Carbonate minerals (i.e. cavities where calcareous crinoid fossils dissolve) Iron minerals (evident as FeO - post depositional iron oxide) i.e. pyrite, hematite, limonite
9	Iron Oxide (FeO) deposits and staining on chert at 40X magnification
10	Inspect for effect on Silica Solubility: pH scale: range from 0 to 14, <7=acidic >7=basic (alkaline) Silica solubility not effected by pH<9 and >2 Ocean = 8.1-8.3 (mildly alkaline) Streams in arid areas = 7-8 (nearly neutral to mildly alkaline) Streams in humid areas = 5-6.5 (moderately to mildly acidic) Presence of impurities effects silica solubility profoundly
11	Inspect for mineral dissolution and replacement: Low pH water (acidic) encourages carbonates to dissolve, silica can then be mobilized and deposited over time in spaces left by the dissolved carbonates Water pitting Un-replaced patches of carbonate minerals and elements (calcium - Ca, magnesium- Mg) can also be seen in cherts– should appear chemically weathered.
12	Pitting due to prolonged H2O submersion at 20X magnification
13	Carbonate mineral dissolution at 40X magnification: evidence of recent acid etching (pH 3.0), no natural mineral replacement
14	Inspect for chemical alterations of color and texture: Consistent with that seen on naturally weathered hand samples collected in similar environment?
15	Inspect for presence of suspicious substances: Look for evidence of oils, stains, waxes, suspicious residues Uniform coating? High spots show wear through the coating?
16	STEP 2 - REVIEW MECHANICALLY INDUCED PROPERTIES
17	Look for evidence of the method of manufacture: Hard or soft billet percussion? Evidence of recent use of copper or other metal tools? Presence/absence of pressure flaking (hard or soft tool flaking?)
18	Presence of copper residue from modern notching tool
19	Inspect for evidence of recent fracturing: Crushing in notches Step fractures (“hanging flakes”) with no patina beneath and/or exceedingly loose or prevalent
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21	Step or Hinge Fracture? What’s the difference?
22	Results of recent flaking: fresh tear lines and loose step fractures, or “hanging” flakes
23	Inspect for evidence of slab preform: Presence of saw marks, flat areas on face of artifact? Unusual uniformity in thickness?
24	Review abrading, grinding & use-wear: Presence of polish (i.e. phytolithic sheen on hafted microliths)? Evaluate sharpness of lateral blade edges and flake scar ridges Evidence of mechanical grinding, tumbling or sandblasting?
25	Authentic use-wear
26	Modern abrasive wear
27	Evaluate damage to artifact: Due to agricultural implement? Iron oxide (FeO) staining? Ancient impact fracture? Preform failure & re-chipping – ancient or modern? Use of ultraviolet light can detect evidence of modern re-chipping
28	Arrows indicate areas of modern re-chipping
29	Arrows indicate areas of modern re-chipping under UV light source
30	Heat treated material? Though not technically a mechanically induced property, the effect can be the result of man’s intentional interaction with the material. Intentional or unintentional heating? “Pot lidding” present? Consistent with heat treating cultures/typologies in archaeological record?
31	STEP 3 - REVIEW OF TYPOLOGICAL ATTRIBUTES Morphometric analysis: Do the artifact’s attributes fall within acceptable morphometric ranges for the type? Flaking style consistent with type? Cross-section consistent with type? W/T ratio within acceptable range for type?
32	STEP 3 - REVIEW OF TYPOLOGICAL ATTRIBUTES (cont.) Finishing attributes (i.e. basal grinding) consistent with type? Account for resharpening: Hafting area free of use-wear? Plausible material given reported provenance and considering cultural use as indicated in archaeological record?
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