Re: Mineral Definition

In article <[EMAIL PROTECTED]>,
[EMAIL PROTECTED] (Bob) wrote:

> I am stumbling to find a true definition of a mineral, to help me
> figure out if the following are indeed considered minerals:  A bone -
> A shell from a crustacean, Petrifed wood, a fossil, and Coal.  Can
> anyone help out there - thanks - Bob

There is no such thing as "a true definition": actually, the answer will
depend on the audience at which the answer is aimed (a child, a friend who
did not go to school, a teacher, a faculty who is recruiting a
"mineralogist" for a postdoc, etc.) 

Actually, the questionable objects that you submit to us are "rocks" (i.e.
objects composed of several minerals=compounds with a crystal structure
and a defined composition, AND some binding medium of organic or inorganic
origin or composition). Natural oils and mineral waters are also "rocks".

If you put a sample of coal under an X-ray diffractometer, you will get a
broad peak which you will recognize as "unfinished" graphite, but you will
not be able to say to what coal component (vitrinite, fusinite,
collinite...) the peak is due. Same with bone, which is formed of several
Ca phosphates And of collagen, fat, blood. If the bone was fossilized, you
may detect vivianite in it if you see blue stains. 

You should begin asking what is a chemical molecule, a solid, a liquid
crystal, a solid crystal, a compound, a pure compound, a defined compound,
a liquid solution, a solid solution...

The definition of "a mineral" will emerge slowly... and if you are smart,
you will conclude that a "new" mineralogy will emerge soon from the
nanoworld, and that several current mineralogy definitions will need a
revision.

J.J.