It's Crystal Clear: Glass + Crystal = Profits.

Title: 
It's Crystal Clear: Glass + Crystal = Profits.
Author/Artist: 
Zack, Jackie.
Published In: 
The Engravers Journal, v. 31, no. 9, March 2006, p. 22+, ill. 0099-0043
Subjects: 
Bib ID: 
AI67776
Notes: 
Differences in the properties, values, and marking methods of glass, crystal, and optical crystal.