How do I know if a gems or beads in a piece of jewelry are made of glass?

Glass will be cold to the touch as opposed to plastic or acrylic. It will also be heavier.

If you tap the item on your teeth, glass will make a “clink clink” noise, and plastic/acrylic will make a “click click” noise. If you are new to this, I recommend trying both together so you can get a feel for the difference. It's quite noticeable.

I recommend using the “pin test” as a very last resort. Glass will not scratch with a sharp pin, but acrylic and plastic will. If you need to do this, do it in an inconspicuous place that won't hurt the piece.

Determining stone vs. glass is a bit more difficult. Please see the following FAQs for more info.

(What other UV reactive materials are found in jewelry?)

(How do I know if them gem(s) in my piece are glass or spinel?)

I am also happy to take a look if you email me with photos. I can almost always determine the material on sight