As you can see, the so-called “tektite-puzzle” is a complex one. As if this were not bad enough, Mother Nature has added to the confusion by creating in addition to the tektites another type of silica-glass not only found along the very same three great circles sprinkled with true tektites, but also having other features in common with the tektite glasses. At Mount Darwin in Tasmania and at Wabar in the Rub’ al Khali desert of Arabia, large and small fragments of this curious silica-glass have been collected. At Wabar the masses of silica-glass were found in and about the rims of a series of meteorite craters formed in nearly pure sand, as we pointed out in Chapter 4. These meteorite craters are known to have resulted from the high-speed impact of iron meteorites upon the sand dunes of the Wabar site. Since the silica-glasses of Wabar have been found to contain countless spherules of nickel-iron of the same composition as the iron meteorites discovered about the Wabar meteorite craters, it seems quite certain that both the sand of the earth target and the nickel-iron of the falling meteorites were vaporized by the intense heat generated at impact. Consequently, it is natural that these Wabar masses of congealed silica-glass and nickel-iron be called _impactites_. They are silica-glasses, created chiefly from _terrestrial_ materials by the impact of large crater-forming meteorites. This same name is now applied to all silica-glasses believed to have the same origin as those at Wabar. As regards size if not composition, the crater-forming meteorites responsible for the Wabar and other impactites may have been big brothers of the small-fry responsible for the showers of true tektites. Or these big ones may have moved about the earth in orbits distinct from those followed by the tektite swarms but lying in the same plane as one of these swarms. In addition to the curious puzzle of the tektites, meteoriticists have also run up against the problem of “fossil” meteorites or, more exactly, the problem of the _lack_ of “fossil” meteorites. As we have already mentioned, no positively identified meteorite has ever been found in other than the most recent rock layers. With all the mining—particularly coal mining—that has gone on throughout the world in historic times, this fact does seem astonishing.