Tuesday, June 23, 2009
CHALK
Blackboard chalk is calcium carbonate and is used for the manufacture of putty, plaster, cement, and of course, blackboard chalk. Calcium carbonate is made up of Foraminifera, shells of little dead marine animals. It is found in the earth’s crust during all geological periods and is usually formed in thick deposits around marine, or formerly marine areas. There are other types of naturally occurring chalk, including black chalk and red chalk. Chalk, in its natural state, was used by early man in prehistoric times for cave paintings.
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Yikes! After reading this blog, the first image that popped into my mind was the little girls I used to babysit who would lick the chalk off their hands after chalking on the sidewalk. Now I just want to scream "DEAD SEA ANIMALS!!!" Gross. It is really interesting to note that chalk goes all the way back to prehistoric times. That makes chalk one of the oldest writing utensils available to us on a daily basis right? Very cool.
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Isn't eating chalk dangerous? I know many kids use to do that. I might’ve done it myself when I was younger. I really did not know that it comes from dead Sea animals. This is some good information to know about chalks. I some how knew that it had something to do with the plaster or cement.
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