I got curious, so I googled it. There's a company that sells amethyst that claims it vibrates at 32,876 Hz. They do not describe anything about the physical characteristics of the particular rock they measured, which would have an impact on the frequency at which it vibrates.

Another source claims amethyst resonates with the Crown chakra, which has a frequency of 768 Hz. They do not explain how they derived this frequency. 32,876 is not a multiple of 768, and would not resonate with something that vibrates at that frequency.

Yet another source claims that amethyst vibrates at 963 Hz. It does not list any physical characteristics of the rock they measured, and this is not a multiple of either of the other numbers.

Credit to Beadworks Philadelphia for explaining that different objects have different resonant frequencies, even if they're made of the same material! Unfortunately, that credit is revoked because they immediately claim that amethyst crystals can cure or treat medical conditions. Shame.