The pencil is not made of lead, it is made of graphite as the main raw material. Graphite is a dark gray, metallic luster, opaque, fine phosphorous solid. It has a smooth feel when touched by hand. It is one of the softest minerals and is composed of carbon. Scratching on the paper with graphite will leave dark gray marks.
In ancient times, people used wooden charcoal, earth blocks, etc. to draw marks on the stones in order to record the language, but the marks left were too thick and easy to fall off, so people found lead again. Lead is a silver-white soft metal. Lead is affected by oxygen, carbon dioxide, and water in the air, and the surface will quickly become dark gray. Scratches on paper will leave gray marks and draw lead into silk. This is the pencil.
But this kind of pen is not ideal, one is light color, and the other is easy to cut the paper. In the 16th century, graphite was discovered. It was more convenient and cheaper to make pens than lead, so graphite gradually replaced lead, but the name of the pencil passed down.
Note: Although graphite is very soft, it is the same substance as the hardest diamond. They are all made of carbon, but the order of the atoms is different. Pressing graphite to a very high pressure turns it into diamond. The pencil refill is made by mixing graphite powder with clay and drying. Because the chemical properties of carbon are relatively stable, the traces written with the pencil can be retained for a long time.