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Flint and the Patination of Flint Artifacts

Published online by Cambridge University Press:  27 May 2014

Robert F. Schmalz
Robert F. Schmalz
Affiliation:
College of Mineral Industries, The Pennsylvania State University
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Extract

The alteration of black or dark-coloured flint artifacts to produce a white surface is familiar to archaeologists. This patination is attributed to weathering, and was first explained by Judd in 1887. Judd suggested that flint is composed of a felted aggregate of euhedral quartz needles with colloidal (opaline) silica occupying the interstices between the crystalline grains. He postulated that carbonate-bearing ground-water leached the more soluble amorphous silica, leaving minute interstitial cavities in the altered margin of the flint. The multitudes of surfaces thus produced reflect and refract light falling upon or passing through the flint, and the resulting scattering causes the white appearance of the altered portion. Judd cited the white aspect of powdered black obsidian as an example of such scattering effects.

Type
Research Article
Information
Proceedings of the Prehistoric Society , Volume 26 , December 1960 , pp. 44 - 49
Copyright
Copyright © The Prehistoric Society 1960

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References

page 44 note 1 Judd, J. W. (1887); ‘On the unmaking of flints’, Proc. Geol. Assoc., 10, pp. 217–26CrossRefGoogle Scholar.

page 44 note 2 Vincienne, H. (1938); ‘Sur l'altération des silex crétacés dans les sables supérieurs de la Perte du Rhône à Bellegarde’, Comp. Rendu, Acad. des Sciences, 207, pp. 295–7, ParisGoogle Scholar.

page 44 note 3 Oakley, K. P. (1939), ‘The nature and origin of flint’, Sci. Progress, 34, pp. 277–86Google Scholar.

page 44 note 4 Scherrer, P. (1918), ‘Bestimmung der Grösse und der inneren Struktur von Kolloidteilchen mittels Röntgenstrahlen’, Göttingen Nachrichten, Math-phys. Klasse, 1, pp. 98–100Google Scholar.

page 44 note 5 Weymouth, J. H. and Williamson, W. O. (1951), ‘Some physical properties of raw and calcined flint’, Min. Mag. XXIX, no. 213, pp. 573–93Google Scholar.

page 45 note 1 The flint specimen, in thin section, was immersed for 48 hours in a saturated solution of cupric chloride, then washed thoroughly and immersed for 30 hours in a saturated solution of sodium sulphide. After this treatment, the more porous opal was stained black or dark grey by absorbed cupric sulphide while quartz was unaffected.

page 47 note 1 Since the rate of reaction, in general, doubles with each 10°C rise in temperature, the reaction rates observed in the present study should be approximately 60 times the reaction rates at 20°C.

page 47 note 2 Curwen, E. C. (1940), ‘The white patination of black flint’, Antiquity, XIV, no. 56, pp. 435–7Google Scholar.