Mike this is not exactly correct.

Then David put his hand in his bag and took out a stone; and he slung it and struck the Philistine in his forehead, so that the stone sank into his forehead.

The pure white stone was manifested by David's faith in Christ. He hit the head of the Philistines, the Goliath, directly in the 3rd eye. Then the synagogue of Satan fell. Revelation 2.9 and 3.9.