The couple of stones we've seen so far (green and blue) have been stone quality rather than gem quality, so I would assume so. These garnet beads are what I think would work for red, for example, because ruby is so pale in that form.
I'm able to see it in an incognito window (no cookies, not logged in) and on my phone. I've also checked to make sure the privacy settings are public. Can anyone else take a look and see if they find a problem? I don't really know what else I'd try.
Screengrabs of the rings from the trailer:
Moiraine taking off her hood
Stepin kissing Karene's ring (we assume)
Karene healing Moiraine (the clearest picture I was able to get)
Alanna drawing Power to stop arrows, hand upside down
Side and somewhat upside down view on a Red