This article explains the glass material that SAW touch screens are made from

Elo's IntelliTouch Surface Acoustic Wave (SAW) touch screens are made of soda lime glass. This is the most common type of glass used in the production of consumer goods and building materials. It is called "soda lime glass" because it is primarily made from soda ash (sodium carbonate), lime (calcium oxide), and silica (silicon dioxide).
 

Soda lime glass is known for its low cost, good optical clarity, and high thermal stability. It is used in a wide variety of applications, including windows, mirrors, containers, and consumer electronics. 

See related article: How Intellitouch/SecureTouch Technology Works