Todd Linton, age 10, of Oromocto, N.B., Canada, for his question:
How do they make graphite?
Graphite may seem rather humdrum and ordinary. As we all know, it is the soft sooty material inside our pencils. It also is used in electrical gadgets and to line certain furnaces, to oil locks and perform other everyday chores behind the scenes. All these workaday duties are the final end of its long life. The creation of graphite is a fascinating story, for the soft sooty material is related to the earth's most precious gem stone.
Some graphite is found in the ground, and some is man made. However, the man made graphite is copied from nature's recipe. Actually, it only speeds up the last stage of the earth's long patient process. Most deposits were started more than 200 million years ago. This was before the arrival of mammals, birds and even dinosaurs. But there were already swampy forests of giant ferns and weird straggly plants.
Through the ages, this ancient vegetation was buried in the ground. And the earth's crust was remodeled again and again. Plants, as we know, are made of a vast assortment of different substances. Gradually most of the materials were removed. The buried old forests were crushed into spongy peat. After millions of years it lost all but plant materials such as gums, woody cellulose and carbon. At last the old debris became buried layers of precious coal.
In some regions, the ancient coal deposits went on changing. This usually happened where the earth's crust was heaved by growing mountains and volcanos erupted layers of seething lava. Heat and pressure consumed the last of the burnable substances, leaving only the ancient carbon.
The atoms of sooty black carbon were crushed into flat sooty fragments and finally the old coal forests became deposits of graphite.
Nature's patient graphite recipe takes countless ages and many dramatic upheavals in the earth's crust. Man made graphite uses the same recipe with a shortcut. The main ingredient may be coal, which is heated in a slow, airless furnace to create a hot, smokeless fuel called coke. Coke also may be made from the leftovers from petroleum, after gasoline and numerous other valuable substances have been extracted.
To make graphite, the hard crusty coke is heated to 3,500 C. degrees in an electric furnace. This terrific heat drives off everything but the carbon atoms and arranges them in slippery flat fragments. In nature, this final process takes millions of years and usually involves mountainous upheavals in the earth's crust. Man made graphite completes this final stage in a few hours.
Sooty graphite is soft and slippery because its atoms of carbon are arranged in flat fragments. But the earth also can arrange these self same carbon atoms in crystal formations. When this happens, they become sparkling diamonds. The glittering clear diamond is by far the hardest of all the earth's natural minerals. Soft sooty graphite is one of the softest yet both are forms of pure carbon.