While I realise the "I can't believe..." comment was a joke , I shoudl perhaps clarify ( forgive the intentinal pun on butter!), what crystal means....and here we get a bit technical.
To be recognised as "crystal glass" according to Britsh Standard 3828 (1973- Definition of Crystal Glass, and
EU Crystal Glass products 69/493 EEC 19th March 2002 Gazette no 24700)a glass must contain Lead, Barium, Zinc or Potash combined or alone of at least 10 %, it must have a refractive index above 1.520 ( that is the amount of light it relects ie sparkle), and it must have a density above 2.54 grms per cm2. Onl;y then can it be called "crystal".
"Full lead Crystal, or "cristal superieur" in French, "Beli Kristall" in German must contain 24% lead at least, amny of the Stourbridge firms added 30-35% lead oxide to get the best cutting softness, sparkle and clarity!
However, I belive most manufacturers have dropped the word lead completely or say "lead free", ( ie Waterford Crystal, and Dartington Glass,)but that does not mean "non toxic"!
Sorry if this is a bit anoraky, but as glass lovers, it may helpthe mebers of this Forum, all being glass lovers, to know the specific and legal definition of "Crystal glass"