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Re: calcium tablets

> Date: Sat, 17 Feb 2001 07:46:26 -0700
> From: "Roger S. Miller" <rgrmill at rt66_com>
> Subject: Re: calcium tablets
> A reader previously wrote:
> > >What about blackboard chalk pieces ?
> Blackboard chalk was traditionally pure CaCO3.  Two or three years ago I
> suggested chalk as a source for calcium and Paul Sears pointed out that
> chalk these days isn't always CaCO3.  I checked what I had; it wasn't. 
> Check yours before you try using it.  If it is CaCO3 then it should fizz
> when hit with a drop of vinegar.
> If you find some blackboard chalk that is CaCO3 then it should be a
> useful source of calcium.

I found on the crayola support that chalks can be (primarily?) :

CaCO3 + clay when extruded
Plaster of Paris i.e. CaSO4 when moulded

> Roger Miller
> ------------------------------