Gemology, the study of precious stones, is not the precise science that some of its practitioners would wish you to believe. Glass diamonds and plastic pearls litter the history of jewellery and though modern science is making such frauds more difficult, some of the more esoteric stones still provide profitable fields for the dishonestly inclined.
In view of the above, gemologists must hold me excused if my admiration for their skill is mixed with equal proportions of scepticism. The man who can glance at a stone and confidently pronounce it to be pure Chinese jade or perfect African sapphire is clearly an expert, but equally obviously must occasionally make a mistake.
It would seem that one of these experts made just such a mistake when assessing some of the treasures of Tutankhamun.
The task of clearing the tomb of the boy-king took nearly four years and was not helped by interference from the Egyptian government of the time. One by one the objects inside the tomb were brought to the surface, examined, opened (if appropriate) and catalogued. Object number 267 was a small wooden chest that turned out to contain, among other things, a pectoral, an elaborate necklace. The centrepiece of this pectoral was a scarab carved out of a greenish-yellow stone that Carter identified as chalcedony.
For some reason a group of Italian researchers have recently studied this particular pectoral and subjected the scarab to a measurement of how it refracted (or bent) light. Their conclusion was that the stone was certainly not chalcedony. A quick scan through the tables of refractive indices showed that the material was, in fact, silica glass - that is, glass made out of sand.
You or I might have grinned sardonically and concluded that some ancient jeweller pulled a quick one on his monarch. The Italians, fortunately, were more thoughtful. They did a few more tests and concluded that the glass was not manufactured, but was in fact natural glass of a type that only occurrs in the remote Great Sand Sea to the west of the Nile Valley. Vincenzo de Michele, a geologist who aided in the study, declares:
"Its origin is probably celestial, caused by the impact on the sand of a chondritic meteorite or comet. The glass is scattered over a 15-mile diameter area, but unfortunately, no crater has been found yet."
It is possible, of course, that there is no crater. A low-alititude explosion of a meteorite or small comet could produce sufficient heat to melt surface sand, which would then cool rapidly, thus producing this particular type of silica glass.
The only problem is that the site where this glass is found is some 500 miles from the Nile, with only the occasional oasis to provide water and sustenance along the route.
We know that the Egyptians showed considerable resource and initiative in exploiting deposits of gold and emeralds in the Eastern Desert, the rugged, parched mountains between the Nile and the Red Sea. Our plane flies over the fringes of this desert as we travel down from Cairo to Luxor and the tangle of dry wadis and rocky cliffs visible from the plane is enough to give anyone a nightmare. We can only admire the enterprise of the ancients that led them to explore and exploit this hostile environment.
Soon after taking off from Luxor on the way to Abu Simbel we cross from the eastern bank of the Nile to the west, where the country is as dry and barren but even more filled with sand. Rocky outcrops protrude above the sea of golden sand, shimmering in the heat as the sun beats down with oppressive weight. The thought of wandering beyond the horizon in this horrific landscape on the off-chance of finding something valuable is beyond my imagination, yet clearly Egyptian prospectors or hunters did precisely that.