Fulgurites @ home
When lightning strikes sandy ground, the sand is molten to form a hollow tube called a fulgurite. I always wanted to find one, but as you can imagine, chances are very low.
But wait a minute - I can make my own lightning! Well, I don't have a surge generator able to produce voltage and energy suitable for melting sand, but using my 4 MOT power supply I can draw a hot arc...
Image by ficusdesk via Flickr