www.mendhak.com/80-the-13-crystal-skulls.aspx (external - login to view)
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Hewlett-Packard experts analyzed the skull and discovered that it consisted of three or four joints grown together. After close analysis, they found out that the skull had been cut of one piece of crystal, together with the lower jaw. The rock crystal has a hardness that is slightly lower than that of topaz, corundum, and diamond; it can be cut with diamonds only. It is astonishing, but the ancient Indians managed to cut it somehow, and even made a lower jaw with the joints. Someone had made the skull of a whole crystal so carefully that it seemed that nobody had ever touched it. A kind of a prism was found at the back bottom of the skull; any ray of light that strikes the eye-sockets is reflected there. If you look into the eye-sockets, you may see the whole room reflected.
Hewlett-Packard experts say that the skull had been made regardless of all laws and rules. They surprisingly said: "The damned thing can't exist at all. Those who had done it had no idea of crystallography or of fiber optics. The people completely ignored the axis of symmetry, which was to prevent the crystal from splitting during processing. It is strange why it didn't split at that!" No matter how unbelievable it may seem, the strange crystal skull can be seen in the Museum of American Indians
I love the "its unlikely people spent 300 years working on them"
Why? I see this alot with archaelogists. In one show they said that even though possible, the obelisks couldn't have been made with tools available at the time, as it would take months or years of backbreaking work in the desert sun to complete.
Apparently they don't get the concept of slavery and why being a slave sucks..