Why have some historians called the Gupta's period a stone age?

Some historians have referred to the Gupta period as a "Golden Age" rather than a stone age. This is because the Gupta dynasty was known for its advancements in art, science, literature, and philosophy, as well as for fostering a period of peace and prosperity in ancient India. The Gupta period is also noted for its significant contributions to mathematics, with the concept of zero being developed during this time.