The origin and occurrence of graphite in the Central Mineral region of Texas have been described by Barnes, Comstock, Dube, Paige, Baker, and possibly others. The following excerpt from Barnes explains the most logical origin of the pre-Cambrian graphite when compared with field conditions:

"Graphite is very common in the Packsaddle schist of Llano and Burnet counties. This schist series was originally a sedimentary series composed mostly of argillaceous, calcareous, arenaceous, and carbonaceous sediment mixtures. This series, before metamorphism took place, probably was very similar to the Pennsylvanian rocks of north-central Texas. The carbonaceous material changed into graphite during the metamorphism to which these pre-Cambrian rocks were subjected. The graphite content of these rocks varies in amount, as did the carbonaceous material in the original sediments. Many of the graphite schists of this area contain insufficient graphite to be of commercial value, while others contain abundant graphite."

Sidney Paige wrote the following concerning the origin:

"As the series of pre-Cambrian rocks described above were in part originally shales, sandstones, and limestones, they are now represented by schists of varying composition. Moreover, certain constituents have become, through metamorphism, of possible economic importance. Such is the change of carbonaceous matter originally in the shales to graphite."