I remembered where I had read it. It was in "The Brothers Karamazov" and two characters (I think one was Alyosha) exchanged their crosses with each other. One cross was made with valuable materials and the other was plain and simple. It's been quite a few years since I read the book so I guess some vague memory of that scene remained even though I can't tell you much else about what happened in the story.
So it's an Orthodox custom, I guess.
It's funny how people snap to the assumption that something is from the NO culture if they haven't heard of it.