Quote Originally Posted by Gerald C Koch View Post
Unused blued steel razor blades like the old Gillette ones are sort after by people who are into crystal radios because they act as diodes. With some wire for an antenna and a ground connection, a headphone, a safety pin for a whisker and you have a radio.
You can buy blued steel in strips, by the foot or by the mile, from places like McMaster-Carr. They make a really insensitive detector, though. Galena and pyrites are better, the crystal radio DXers are using Schottky diodes.