Ask A Scientist General Science Archive

Author:     olson6
Text:      Our Science book (Addison Wesley Science-Grade 4) says that 
minerals are solids that form from one or more chemicals and are not living 
nor do they come from living things.  It also says that rocks are mixtures of 
minerals.  If that is so, then why is limestone considered a rock when it 
comes from crushed shells which were one time living things.  Also, if coal 
can be pressed into diamonds, and coal comes form the remains of dead plants, 
how can diamonds be considered minerals?

Response #:  1 of 1
Author:      Robert Topper
Text:        Good question, olson6.  I think that your book's definition of a 
mineral is too narrow, and I agree with you.  I think of a mineral as a solid 
which is created by natural forces and is a chemically pure substance, which 
means that it only has one kind of chemical compound in it.  So diamond, which 
is made of carbon, would be a mineral, and so would limestone, which is made 
of calcium chloride.  But a rock which was a mixture of limestone and granite, 
for example, would not be a mineral, but just a rock.  It is fun to think 
about where things originally come from, for example, as you said, coal can be 
pressed into diamonds.  (At least, Superman can do it!).  And coal comes from 
the remains of dead plants, primarily carbon with other stuff.  But their 
carbon was ultimately formed in the heart of a sun, which is not a living 
thing...