Re: And another definition..

"Landy" <[EMAIL PROTECTED]> wrote in message news:<[EMAIL PROTECTED]>...
> Bob,
> Here's the definition(s) we give our first years (you'll find something
> similiar in most first year university level Geology texts)
> 
> MINERAL
> A naturally occurring solid possessing a characteristic chemical composition
> (or range of compositions) and a systematic 3-dimensional atomic
> (crystallographic) structure.
> 
>  e.g. quartz SiO2
>   pyrite  FeS2
>   calcite CaCO3
>   olivine (Mg,Fe)2SiO4
> (the last example explains why the "or range of compositions" bit is in the
> definition - it accommodates the solid solution found in many minerals)
> 
> CRYSTAL
> Any mineral grain bounded by natural planar surfaces (i.e. crystal faces.)
> 
> ROCK
> A naturally occurring, coherent, multigranular aggregate of one or more
> minerals.
> 
>  e.g. granite, sandstone
> 
> Quite clearly, petrified wood, fossils and coal are all rocks rather than
> minerals.
> Hope this helps,
> cheers
> Bill
> 
> 
Thanks, it did!
Bob