Jalisco or Xalisco or both

I was reading an article on the Primavera Forest just out side of Guadalajara and it mentioned that the major rock formation is of volcanic ash hardened into pumice, also known as Jal.   This pumice formation is one of the largest in the world and gave rise to the state name of Jalisco.

With only that one reference I wasn't convinced that Jal was even a word let alone the origin of the name.   Looking further I did find a few well respected authors making the same claim.   Jal is also used in advertisements when sold for industrial purposes.

So what can you do at this point but search Jalisco and up pops Wikipedia with it's version which is:

The name is derived from the Nahuatl Xalisco, which means over a sandy surface. Until about 1836, the name was spelled “Xalisco,” with the “x” used to indicate the “sh” sound from Nahuatl.

Could the sandy soil and pumice be one and the same