[jshepherd]

He said he hit an air pocket and the drill jumped across and went straight through.

From a round? You will only find hollow pockets in non-rounds. He likely hit the conchiolin layer on the opposite side just before reaching the opposing nacre. When this happens you do feel the slip, and m.o.p. dust jumps out of the drill hole. This is the perfect spot if you are using a swivel drill and intend to flip the pearl around and come in from the other side. You are completely through the nucleus at this point, and you will not chance cracking the pearl.
I have actually done the same thing as your driller many times, accidentally coming through the other side - just pushed it a little too far. If one is lucky it will not damage the nacre. But it often leaves a crater.

You will find out what the secret is in G&G, but only if you really read between the lines. We were not very overt in that article. Just stating the fact... in a scientific sort of way. I will post an article here as well as soon as I receive my regular mail G&G. The Pearl-Guide article won't hold any punches.

I have heard that the Philippines may be on the next agenda. Jewelmer would be a great host.