What is the stone used.. (wiccan)?

My ex-girlfriend, sister and friends mother all believe in supernatural/paranormal and They all practice in Wiccan activities. I've partaken in some with my ex-girlfriend and my sister when they hold a pendant of some sort and ask 'it' questions with which is swings either clockwise or anti-clockwise for yes and no or it is held over paper with the words "Yes" and "No" written, and it will swing in the direction of them. I was wondering what the stone is called, and also anything else anyone knows about 'Name' stones and 'Protection' stones.