The rock cycle is the basic explanation of the way rocks are recycled. Essentially the rock cycle is a group of changes, but not all of these changes have to be chemical. For example, sedimentary rocks can become metamorphic rocks through heat or pressure. Then these metamorphic rocks can melt to become magma, when this magma cools it will become igneous rock. Through weathering and erosion that igneous rock can become sediments, and then the sediments through compaction and cementation will become sedimentary rocks again. Thus, the rock cycle is repeated!
Rocks from the Precambrian era are billions of years old. They must have gone through this rock cycle many, many times. This changes the formation of the rock, and it is no longer a rock from the Precambrian era. However, it is possible for a rock to remain at the same stage for a long period of time, for instance in the earth's crust rocks can remain there for a very long time. But, it is very unlikely that a rock from the Precambrian era will surface so that we can see it without going through any of the steps of the rock cycle. But I am sure that it is not impossible.
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