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Have you ever heard the phrase “rock solid?” Rock solid usually describes something that does not and cannot change. This phrase means something is absolutely sure and will not fail or go wrong. A rock-solid plan is a sure bet; it will not change and it will not go wrong. When you see pictures like this rocky mountainside in Costa Rica, it is easy to get the feeling that rocks neither change nor move, and always stay the same.
In this chapter you will find out that rocks do change: from one type to another, to an altered version of the same type, over long periods of time, or more rarely, in a short time. This Costa Rican hillside’s days are numbered… and a diamond is not forever.


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