Chalk, though not modern blackboard chalk, is limestone, calcium carbonate. It is found in abundance in the downs and wolds of the UK. Think of the chalk cliffs of Dover. And the Needles. Of course, it's found elsewhere too - in fact, where isn't it found!
The colour (or lack of colour) of chalk comes from the bones and skeletons of ancient sea creatures and fossils are abundant in any limestone. I remember the excitement of finding fossils in a rocky hillside near the train track where I lived in suburban Montreal as a child.
The Channel Tunnel between the UK and France actually goes through one particular layer of chalk called Chalk Marl because it was relatively drill-able, yet strong enough to support a tunnel and its contents.
 |
| @ferrisjabr |
Classroom chalk used to be made of calcium carbonate but is now made from gypsum, which is calcium sulphate. Does anyone even use chalk in the classroom anymore?
Thinking about chalk triggered some thoughts about using the word "chalk" in our language.
- by a long chalk
- chalk it up to experience
- ?
No comments:
Post a Comment