Indus Valley Glass Ancient Bead 4,000 years

Again, a most amazing and ancient Bead. It is glass , with a dent.. Makes me think it might have been in a fire..? It is black with white lines wandering around it. Just to hold it is holding something so ancient and really, in my world, amazing. Comes from my Indus Valley Collection. On a cord with two sliding knots so it can be worn quietly.