<HTML>Anthony,
>>Therefore, it could contain lots of things... but you would need a quartz face that has been cut and exposed to the elements, without being eroded away over time. This would be an impossible task for most of the sphinx, for example, because the body... the contested part of the construction... simply isn't there any more. The surface we see is not the surface that was carved 4600-4900 years* ago.<<
Some of the Member I stone at the base of the Sphinx has undergone very little erosion behind the facing stone and would still be useful to date, if that can be done. But I agree that the Sphinx may be problematical for this kind of study on account of both its mineral content and the uncertainties and losses associated with weathering.
David</HTML>
