If the glass is uncolored, you can tell which one it is by looking at a thick layer of it (e.g. along the sides): soda-lime has a green-blue tint, while borosilicate is more yellow: Borosilicate: [![enter image description here][1]][1] Soda-lime: [![enter image description here][2]][2] If you don't mind shattering the jar, you can always test it: put some ice cubes inside, wait until the jar is cold to the touch, and then pour boiling water on the outside (or put the jar in a pot with just boiled water). Borosilicate glass will not crack, soda-lime will. [1]: https://i.sstatic.net/6vIyx.jpg [2]: https://i.sstatic.net/wZg3z.jpg