Which of the following materials was mainly used in the manufacturing of Harappan seals?

Most of the seals were made of steatite, which is a kind of soft stone. A few of them were also made of terracotta, gold, agate, chert, ivory and faience. The standard Harappan seal was square in shape with a 2X2 dimension. It is believed that the seals were used for commercial purposes.Most of the Harappan seals were made up of terracotta on which inscriptions and animals engrave on them.