The tools found in the deeper layers of the Klipdrift Shelter that represent the earlier phases of the Howiesons Poort were found to be made from heat-treated silcrete
, while those from later phases were made from less homogeneous rocks such as quartz and quartzite.
FIND: The Blombos Cave drawing with ochre pencil on silcrete
It consists of three red lines cross-hatched with six separate ones created by an ochre crayon on a silcrete
rock undergoes a number of readily identifiable physical changes upon heating, including reddening (Schindler et al., 1982), loss of porosity (Schmidt et al., 2013b), occasional heat fracturing (Mercieca and Hiscock, 2008), and increased brittleness (Domanski and Webb, 1992).
Kelly, J.L., Fu, Bin, Kita, N.T., and Valley, J.W., 2007, Optically continuous silcrete
quartz cements of the St.
Langford-Smith T (1978) 'Silcrete
in Australia.' (University of New England: Armadale, NSW)
A geoarchaeological study of silcrete
in the Central Queensland Highlands highlights the importance of geological context in understanding the procurement, use and transport of artefacts.
This was a time period when the energy from floodwaters was very high; large cobbles were pushed across the landscape during flood events and it appears early assemblages of flaked silcrete
artefacts were polished and sub-rounded to then lie exposed for millennia in brachiating creeklines fringing the lake.
They have been denoted with different names such as silcrete
in the USA; talpetate in Nicaragua; hardpan, duripan, and cangahua in Colombia and Ecuador; cancagua, moromoro, tosca, and nadis in Chile; hardpan in Peru; and kora and masa in Japan .
7 Nature by archaeologist Kyle Brown of the University of Cape Town in South Africa and his colleagues--were made from a type of stone called silcrete
that had first been heated to make the rock easier to chip.
From this work, Toro has identified up to seven sand units above the basement and below a confining upper silcrete