Microstructure of Flint and Other Chert Raw Materials*

Abstract

The crystallite size, microstrain, stacking disorder and moganite content of flint and other chert raw materials were studied by X-ray powder diffraction profile analysis. The broadening of the X-ray reflections of all microfibrous quartz varieties is due to both anisotropic small crystallite size and anisotropic microstrain. The microstructure varies for samples of different origin. The moganite content and the number of structural defects are higher in flint than in older chert and petrified wood. The X-ray diffraction pattern of the cortex of flint differs from that of the core material, whereas those of the patina and the unweathered interior of the rocks do not.

Driving forces for the weathering and alteration of silica in the regolith: Implications for studies of prehistoric flint tools

“…It is widely observed in diagenetic and weathering environments that successive transformations of silica phases generally results in increasing crystallinity and decreasing solubility (Goldstein and Rossi, 2002;Graetsch and Grünberg, 2012;Knauth, 1979;Lee, 2007b;Willey, 1980;. Once precipitated the silica crystal begins to increase in size, resulting in a decrease in surface defects and a more compact structure (Moxon et al, 2006).…”

“…It is a consequence of differential alteration: the most soluble silica phases are dissolved whereas more stable phases and of better crystallinity than in the primary one are preserved and/or precipitated (Graetsch and Grünberg, 2012). The silica coating remains partial and discontinuous on flints contained within colluvium.…”

The chert from the Castelltallat Formation (south-central Pyrenees): archaeometric characterisation and archaeological implications

“…It must be borne in mind that moganite is a metastable phase of silica that appears in chert of different origins, ages and sedimentary environments, both marine and continental (Heaney and Post 1992;Graetsch and Grünberg 2012). Although moganite is often associated with arid environments, it is not of special significance when it amounts to less than 20% of the total rock volume (Bustillo 2002).…”

In the footsteps of Pliny: tracing the sources of Garamantian carnelian from Fazzan, south-west Libya

“…Yonekura 2008; Tsobgou 2009); crystal properties and moganite content by X-ray diffraction (e.g. Pretola 2011; Gliozzo et al, 2011;Graetsch and Grünberg 2012); and petrological issues (e.g. Bustillo et al, 2009;Machado et al, 2013).…”