Most interesting Steve. I would assume that most Sandstone fireplaces in Southern KY were not burning fires much over 500 degrees, or some other mineral such as iron found within the rock was somehow preventing the destruction. I believe several historic Iron furnaces and smaller kilns were constructed of the same Pennsylvanian (time period not state) sandstone. 

Larry2

---- [log in to unmask] wrote: 
>  
> In a message dated 1/17/2010 11:52:11 A.M. Eastern Standard Time,  
> [log in to unmask] writes:
> 
> So they sort of flake off?   I had supposed they popped off  (whether from 
> trapped steam or lateral expansion on the exterior.)    In New York, you can 
> often tell see the tell-tale marks of when a building  (especially a loft 
> building) has gone upscale.   The (almost always)  granite watertable, 
> although immaculately cleaned and pointed, in concert with  the million dollar 
> lofts upstairs, has multiple episodes of  scaling, evidence of frequent fires 
> where the trash was collected, since  the (long-gone) 
> homeless/delinquents/etc. set it on  fire. 
> 
> 
> 
> That's most of it.  Spraying cold water on the hot rock tends to help  the 
> deterioration along.  
>  
> The quartz is microscopically beautiful because of the alpha-beta  
> transition fractures that occur in a fire.  The quartz is decorated  with a series 
> of concentric, rainbow-colored shells.   The rainbows are due to iridescence. 
>  It is much prettier than the  shocked quartz from meteorite impacts that 
> National Geographic puts into  dinosaur and K-T boundary articles.  The 
> beauty of the broken quartz might  even be a religious experience.   It is 
> certainly more enlightening  than many of the religious experiences that I'm 
> supposed to have had.
>  
> Steve Stokowski
> Stone Products Consultants
> 
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