My wife has an empty cosmetics jar. It's quite small and looks and feels very much like cut crystal glass. The fingernail test says glass, but the tooth test says plastic. Any idea what it could be?
Probably polycarbonate – it's used to make pub glassware, spectacle lenses, eye-protection and Covid shields. There must be several grades because lemonade bottles are made of it too, and they're nothing like glass.
"Crystal" styrene would probably be the popular choice for an optically clear moulded product.. it's probably the only polymer that is clear enough / has the most convincing refractive properties to look like glass.. you'll be able to tell if you can burn a fragment of it – it's distinctively acrid..
I have made perfume top moulds in my working life. Crystal Styrene is a possibility, when making the tooling we where told the moulding material was "Acrillic"