Marble is formed by intense heat and pressure (metamorphism) acting on any type of limestone. The metamorphism tends to cause an increase in crystal size which is why most marbles have that sugary texture and consequently take a good polish. The colors and textures are as varied as the types of limestone from which the rock formed. Travertine is a layered deposit of caclium carbonate that precipitates from geothermal waters. You can see nice examples happening today at Yellowstone. Travertine often has large pores as it is simply depositing in open spaces. However, as it often has coarse crystals it may take a good polish and that is why many in the stone industry do not distinguish it from marble.
John
----- Original Message -----
From:
[log in to unmask]Date: Wednesday, November 12, 2008 8:45 am
Subject: [BP] Ribbon slate
To:
[log in to unmask]> Ribbon slate ; nice to look at but my guess is you won't find
> very many 100
> yr old samples of it on roofs any more .... the "ribbon" is as
> john descibes it
> below apears as banding but in fact the particles are more
> open and angled
> and therefore open to the weather ;
> and I wouldn't get too fussy about hearth stone if its a
> working hearth (vs
> a decorative hearth ) somehow I can't see Bill gates splitting
> the kindling on
> his
> Ohio Sandstone ; and You can forget using Travertine ; Back in
> the day these
> stones were at least 3'' in thickness I would opp for the slate
> or granite
> and stay away from tile unless your Martha Stewart and you are
> eating off of it
> .
>
> Ps John ;if its not too much trouble go into the geological
> difference
> between travertine and Marble .....Py
>
> John writes
>
>
> > However,
> > >these new platy minerals orient themselves at a high angle to the
> > >direction
> > >of the compression. This is what produces the cleavage or
> rift in a
> > >slate.
> > >If you look closely at some slates you will often see a faint
> banding> >across
> > >the split face. This is the original bedding orientation
> that is now at
> > >an
> > >angle to the rift. It's best observed when there are sandier
> layers> >present. If you get a little hotter and squishier the
> slates will first
> > >become something called a phyllite, then a schist, then
> finally a gooey
> > >mess
>
>
>
>
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