A natural diamond is made from carbon and is the hardest natural known substance on earth. Natural diamonds form under intense heat and pressure conditions existing between 85 to 125 miles in the earth's mantle. A natural diamond can be called a real diamond if it is a certified natural diamond. Shop our natural diamonds engagement rings. Customize your engagement ring, with the fancy color pink, blue, brown, yellow diamonds. Feel free to change the setting or gemstone to any colored gem of your choice if needed.