By Eddy Montilla
We frequently use things without thinking how they come to our hands. Chalks, something that we used for so many years at school, are a good example of them. And now, this is the answer: Chalks are made of calcium carbonate and gypsum powder that during a process solidify into a bar. These days, you can also find eggshell chalks and others, an excellent way to recycle things and protect the environment.
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