GIA DIAMONDS/DIAMOND GRADING 4-6

Diamonds were delivered to the earth's surface as recently as A. 20 billion years ago. B. 20 million years ago. C. 1 million years ago. D. 10,000 years ago. - Answer-B. 20 million years ago. The three main components of the earth are the crust, mantle, and A. core. B. center. C. stratosphere. D. subduction zone. - Answer-A. core. How far beneath the earth's surface do diamonds form? A. 15 to 30 miles (25 to 50 kilometers) B. 30 to 50 miles (50 to 75 kilometers) C. 50 to 90 miles (75 to 140 kilometers) D. 90 to 140 miles (140 to 220 kilometers) - Answer-D. 90 to 140 miles (140 to 220 kilometers) The correct conditions for diamond formation exist under A. cratons. B. volcanic ash. C. oceanic crust. D. large mountain ranges. - Answer-A. cratons.