Re: Yes, there is a Mineral Definition

"Carl 1 Lucky Texan" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
> So what is opal?(or even tabisheer?) or obsidian?
Opal is often referred to as a "mineraloid", since it has a restricted
compositional range but does not have a crystalline structure (it is
amorphous).  Obsidian (also amorphous), on the other hand can have a huge
range of compositions, and is therefore a rock -  note if allowed to
crystallize it would for a felsic igneous rock of some sort (e.g. dacite,
rhyolite, granite).  And sorry, I've never heard of tabisheer?
cheers
Bill





>
> Carl
> 1 Lucky Texan
>
>
> Fred_Miner wrote:
> > DEFINITION OF A MINERAL:    A mineral is a natural, homogeneous,
inorganic
> > solid with a crystalline atomic structure. Crystallinity implies that a
> > mineral has a definite and limited range of composition, and that the
> > composition is expressible as a chemical formula.
> >
> >
> > From  http://www.mine-engineer.com/mining/mineral/mineralindx.htm
> >
> >
> > Bob perhaps you could stumble into the library, next time, or are they
out
> > of fashion now days.
> > The other day I was wondering, are there parallel dimensions around us,
or
> > are they just figments of my imagination , , ,
> >
> >
> >
> >
> > "Bob" <[EMAIL PROTECTED]> wrote in message
> > news:[EMAIL PROTECTED]
> >
> >>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
> >
> >
> >
>
>
> -- 
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>