Analysis of burnt bone:

Discovering the circumstances of burning

Why study burnt boneMany UsesUse of fire in prehistory, dietary and cooking

habits, animal sacrifices, migration and trade in life stock, firing of cities, cannibalism, witch executions and funerary practises

2 Questions• What are the bones?• What are the circumstances of burning?

What are the Circumstances of burning

• Temperature• Time• Soft tissue• Oxidation• Other objects (metals)• Location

Analysis techniques

• Colour• Fracture patterns• Elemental analysis (ICP-MS/XRF)• Other analytical techniques (XRD,FTIR,

electron microscopy)• Use of external clues

Fracturing

Colour & TemperatureStage Temperature range Colour description Munsell

(dominant colour)

1 20-285 °C Neutral white/ pale yellow 5Y 8/2, 10YR 8/4

2 285-525 Reddish brown, dark grey brown, neutral

dark grey, reddish yellow

N 2.7 5/0

7.5YR 8/3

3 525-645 Neutral black, medium blue, some reddish

yellow

10YR 7/2

4 645-940 Predominately neutral white, with light

blue grey and light grey

N 9/0

N9.5/0

5 940+ Neutral white with some medium grey and

reddish-yellow

N9.5/0

Colour & Metals • Characteristic colour for

each metal:e.g.• Bronze: Green/Blue• Iron: Red• Zinc: Yellow

Problems with colour analysis• Secondary change• Many confounding variables

External clues• The melting of another material with a known or

calculable melting point• E.g. Glass melts at 500°C to over 2000°C depending

on the type of glass

Elemental analysisUse:• Identification of

compounds or elements• Good at detecting

staining- Metals/ minerals

• Thermal decomposition

Examples:• XRF• ICP-MS

Other analysisUsesDistinguishing burnt from

unburntLooking at the degree of

burning:• Recrystallization• Thermal decompositionPenetration of staining

Examples• XRD• FTIR• Electron Microscopy

XRD

In

te

nsity

2-Theta - Scale

21 30 40 50 60 70

NaCaPO4, CaO, MgO

BibliographyShipman, P., Foster, G. and Schoeninger, M. (1984).

Burnt Bones and teeth: an experimental study of colour, morphology, crystal structure and shrinkage. Journal of archaeological science, 11, pp.307-325

Harter, R.(2011). Piltdown man. http://home.tiac.net/~cri_a/piltdown/piltdown.html

Nicholson, A.(2011). The effect of multiple burning on bone mineral