The History Channel and the Crystal Skull

I saw the movie, actually Indiana Jones and the Crystal Skull.  Fun flick with some good scenes, like Harrison Ford and Shia LeBeouf riding a Harley thru the Yale library reading room.  Later they discover an alien crystal skull which becomes a clue that leads them to lost cities and so on.  Great movie prop.  I had never heard of crystal skulls before and I assumed it was a product of  Spielburg's fertile imagination.
   So the other night I am channel surfing and on The History Channel I find a "serious" documentary on crystal skulls.  Ten of them are known, the show had some pictures, and claimed that one had been scientifically analysed.  Groovy.
   Of course the show didn't say whether these skulls had been discovered before or after the Spielburg movie.  Nor did it say what the "scientific analysis" had discovered.  For openers, what was it made of?  Quartz? Glass? Calcite?  Rock salt?  Lucite?  The History Channel was less convincing than the Spielburg movie.