A diamond's splendor has been appreciated for centuries, but there was not much scientific knowledge about it before the twentieth century. In fact it was a big jewelry mogul that used the phrase "a diamond is forever" in the late 1940s that catapulted this beauty into popularity. As a work of nature, the diamond is pretty amazing. It's the only gem made of a single element: It is typically about 99.95 percent carbon. A diamond is also the hardest material on earth: 58 times harder than anything else in nature. The only thing that can scratch a diamond is a diamond! The diamond is recognized today as the birthstone for April, and is also the gem that marks the 60th and 75th wedding anniversaries.