Originally Posted by onelove

The only place this would be a problem is LHR with a no cary-on policy. Elsewhere it would be business as usual. If one is transporting loose diamonds they could be carried in concealed waist and vest pouches. They will not set off the metal detector and could be revealed and inspected in a private screening if detected in a pat-down.

The alternative is shipping via fedex or a similar private courier. The costs, including third-party insurance, are pretty steep but it would be better than nothing.