<HTML>Miss. Morris cites from one of Davidovits' papers below I think... the "volcanic silica" (which I suspect is a.k.a. volcanic glass) pops-up a few times. One would expect to see at least some volcanics dispersed in a shallow marine carbonate limestone like the Mokattam Formation.
"Importantly, chemical analyses of this white coating show the same unusual mineralogy as the bulk of the Lauer sample. These minerals include apatite, brushite, a volcanic form of silica, and a very small amount of the synthetic zeolite ZK-20. It is not usual for zeolites to form during the natural geological formation of limestone. The zeolite crystals are more likely the result of a subsequent chemical reaction, geopolymerization. The synthetic zeolite ZK-20 occurs when natron is reacted with organic ammonium. The ammonium can come from urine or collagen from flesh or bone."
"A small limestone sample from the outer casing of the Pyramid of Teti was provided by Egyptologist J.P. Lauer. The sample was chemically analyzed by two different laboratories, one in France and another in Belgium. Like the sample from the Great Pyramid, the Teti sample shows a zeolitic mineral from the same levynite group. Volcanic silica and brushite (organo-calcium phosphate, which occurs in bone, dung and teeth) are also present."
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