Others are used widely in industry. The color of a diamond depends on the kind of impurities embedded inside it. Yellow diamonds, for example, betray minute quantities of nitrogen, while boron imparts a bluish hue. There are other inclusions in diamonds that have great scientific value. Such samples are time capsules that yield valuable information about conditions deep in the Earth's upper mantle where diamonds formed, and yield clues to the formation and age of the diamond.
Diamonds are the rich cousins of graphite, both crystalline forms of pure carbon.
The enormous differences in their properties is a result of the way that carbon atoms are bonded together. In graphite, carbon atoms are arranged in sheets that easily slide past each other, making them ideal as lubricants and of course, pencil leads. In order to achieve such a compact and strongly-held network of carbon atoms, it is believed that diamonds must have crystallized deep under the Earth's surface. Such pressures and temperatures reproduced in laboratories have successfully yielded synthetic diamonds. They are also found in sedimentary rock where gravel deposits and organic material have been compressed into rock.