How do I tell guar gum from xanthan? I purchased both guar gum and xanthan gum in little unmarked baggies from the bulk section of my local health foods store.

This was months ago and since I foolishly forgot to label them, now I have no idea which is which. How can I tell? Are there any experiments I can do? Taste tests?

One is slightly darker, but that's the only obvious visual difference.
Guar gum has a particular grassy/earthy/beany smell, whereas xanthan gum is much closer to odorless.