Graphite pencils consist of a mixture of graphite and which other material?

Graphite pencils are made by combining graphite with clay. This mixture is crucial because it determines the hardness or softness of the pencil lead. The process of blending the two materials allows manufacturers to control the properties of the pencil, producing a wide range of grades from hard to soft leads. The higher the clay content, the harder the pencil will be, while a higher proportion of graphite yields a softer lead that produces a darker mark. This combination is essential for achieving the desired writing or drawing characteristics in a pencil.

The other materials listed do not contribute to the lead composition in the same way. Wood is primarily used for the casing of the pencil, not the lead itself. Charcoal, while related to graphite, is not used in standard pencil production, and sand does not play a role in pencil lead composition. Thus, the correct answer reflects the essential components that create the functioning core of a graphite pencil.