A light stone and a dark one hang on this pendulum: a clear quartz crystal pointed at both ends and a jet-black obsidian sphere. The fittings and the long chain are silver-tone. Including the chain it measures about 25 cm, and it was made in India.
Volcanic glass beside quartz
Obsidian is volcanic glass. It forms when lava cools so quickly that it has no time to grow crystals. Polished, it is almost mirror-bright, which makes it look even blacker next to the clear quartz. In the Stone Age its sharp flakes were made into blades and arrowheads.
Black stone and clear quartz contrast in any light, so the movement is easy to follow while it swings.
By tradition, obsidian is a stone of protection and quartz a stone of clarity.
First ask what yes looks like
Many people who work with a pendulum first settle how it shows yes and no. Hold the chain steady, wait for the stone to stop, then silently ask it to show you yes. Notice whether it moves back and forth, side to side or in a circle. Do the same for no.
This movement can differ from person to person, so it is worth writing down. That way you will always know what each swing means in your own hand.
Keep it away from hard floors
Because obsidian is glass, its edge can chip if dropped. Avoid swinging it over tiles, and put it back in a small box or soft pouch after use. Both stones are natural, so colour and translucency vary slightly, and yours will not look exactly like the photo.