I design electronics in my day job..

Printed Circuit Boards are normally made with a fiberglass material. You can get them lots of thicknesses, but common is about 1.6mm (1/16 inch?) think. You could glue two together to build up any thinkness you want. The fibreglass is a pretty ugly translcent yellow/brown/straw colour, but the vivid green colour you see is called a soldermask and is printed onto the board and you can get it in lots of different colours.

This one looks like it was a "spare" board - it has not had any parts soldered to it as you can still see the gold flash on all the pads.

If you are going to work with this stuff, remember that the dust is nasty - just like any other fiberglass. Oh and one neat trick is that you can smooth edges etc with acetone and a cloth rather then sandpaper - it disolves the board material a little and if you do it right you can polish the edge nicely.

Cheers,
Ash.