Phillip, 

Most of the structure is, in spite of the white pictures we normally see, made out of red sandstone.  The designers overlaid the sandstone with white marble.  That was a new innovation for the time and they had to create new techniques for it.

As I mentioned in the article, ornamental materials came from all over India and Eurasia.  The sandstone came from a quarry about 50 miles away.  The marble came from a quarry about 200 miles away.