sentences:  When he called a surveyor out to inspect the land, the surveyor found that the land was solid Goshen stone, a type of mica schist estimated to be about 400 million years old.Estimates have placed the low estimate of the find at 24 million tons.At current prices (he has been selling the stone for over $100/ton), it is estimated to be worth around $2.5 billion, minus extraction costs.