"Thomas de Groot" <t.d### [at] internlnet> wrote:
> "PM 2Ring" <nomail@nomail> schreef in bericht
> news:web.445210571843be3376ba2c900@news.povray.org...
> >
> > Thanks, Thomas. It's always nice to get your geologist's approval of my
> > stones.
>
> Oh hum... <grin>
>
> > Living in Sydney, I've seen weathered sandstone all my life, and plenty
> > weathered by seepage. Sydney basin is built on sandstone and shale. As
> well
> > as the white, yellow and apricot colours of my palette, the real stones
> have
> > some beautiful shades of red, ranging from pale rose pinks to an almost
> > purple colour. I know the reds & yellows come from iron, but I don't know
> > about the purple.
> >
> It very much depends on the minerals in solution percolating through. Iron
> of course, manganese like dlm says. I am not too familiar with that branch
> of the trade. The irony is of course that I am living in a country that is
> very poor in hard rock! But you can get the same kind of staining in sands
> too, especially in the older deposits from the Pleistocene. And sands are
> the building blocks of sandstones, so...

Yes, I was expecting you to be an expert in sedimentary rocks, from your
location. I guess you're attracted to more exotic geography. :)

There's a big tunnel being built here at the moment and my route to work
lets me see most of the constructions. So I've seen plenty of freshly
exposed sandstone lately. Some of the pieces have been beautiful.

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