Above the metallic core of the planet, the lithosphere consists
exclusively of fluorides of the metals. There are no oxides, sulfides,
silicates or chlorides. There are small deposits of such things as
bromine trifluoride, but these have no great importance. Since
fluorides are weak mechanically, the terrain is flattish. Nothing
tough like granite to build mountains out of. Since the fluoride ion
is colorless, the color of the soil depends upon the predominant metal
in the region. As most of the light metals also have colorless ions,
the colored rocks are rather rare.