For a material to be useful to geologists, it has to have a half-life on the order of geologic processes and be around. Datable material favored by geologists Because of the requirement that no child product be incorporated in the material to begin with, the minerals that are favored separate parent from child. Dating minerals in sediments generally will give you the age when the mineral formed - not the sedimentary rock, so geologists favor igneous rocks for dating purposes. Most of the isotopes used for dating were made billions of years ago in a super-nova explosion, like the rest of the stuff we are made of. This could not possibly have survived from before the birth of the Earth and in fact is made in the upper atmosphere by bombardment of cosmic rays.
Carbon is also different in that it is incorporated into organic material.
It is used for dating things like trees, fires, cloth, soils, corals, etc. Putting it all together Over the last few decades, geologists have found datable material in lots of useful places. We now know pretty well how long various parts of the rock cycle take. For example, we know that it takes millions of years to build a mountain and hundreds of millions of years to wear it back down. It takes tens of thousands of years to make a decent soil and only a few years to wash it away.