Dan,
We do not speak of those secrets in public..... Just kidding, you would be surprised the stuff that gets past customs and the stupid things they stop you for.
For instance I was stopped at JFK for Alpha and Beta particle radiation from Galway Granite. Should mention I had about 300 pounds of the stuff :D Made for an interesting afternoon with TSA and Custom Officials.
BTW they said nothing of the plant materials in my suitcase.
Chris