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Re: Blackboard Chalk
Actually it is neither of these materials. Blackboard chalk is made from
the very tiny (less than 5 microns diameter) critters called coccoliths
and they are calcite which is CaCO3 in a hexagonal form.
Just being a "prig" or trying to fulfill by duty to the list.
o Mike Nielsen u
m Department of Geography THE OPTIMIST BELIEVES WE LIVE IN ?
a Harvill Bldg Box #2 THE BEST OF ALL POSSIBLE WORLDS; w
r Tucson, AZ 85721 THE PESSIMIST FEARS THIS IS SO h
e mnielsen at u_arizona.edu