X-ray
The x-ray spectrum is advantageous because its non-destructive and detects elements. Shown is my portable x-ray fluorescence detector which I am just starting to experiment with. It was originally used to detect lead in paint but can produce a spectrum from 10 Kvp to 100 Kvp. This device requires the specimen to be dosed with x-rays in order to work. 
Just seeing what's inside lumps of stuff is cool too. This is my portable x-ray generator from Golden Engineering. Have x-rays will travel!
