In the 1800s absolutely, but since the discontinuation of leaded products, significantly heavy glass with tin, aluminum, titanium or other metals added for strength and sheen has been deemed crystal, with the previous material being designated as leaded crystal.

I’m an avid antique collector and have needed to know the difference for several years.

If you reside in the EU or Britain however, disregard those statements, as they still have legal definitions of crystal on the books.