For me, the worst thing about the use of chalk is the fact that in order to make the mark, people think that it must be easier to break up than the surface that is being worked on.
I beg to differ.
I am sure plenty of us hereabouts have seen with our own eyes the sand found in the locality of sandstone carvings; the effect of weathering, water, ice, even wind. These surfaces can be quite delicate.
Here's an idea - take a bit of chalk and use it to mark a surface which you think is harder, for example your teeth. Now tell me it's not gritty and abrasive.
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