FMF - Friends of Minerals Forum, discussion and message board

[Paul Biehler]

How is it that rutile, brookite and anatase all have the same elemental composition but are so diverse from each other in seemingly every way?

[alfredo]

Different crystal structures. You could ask the same question about diamond and graphite, which have the same chemical composition but are so incredibly different from each other in appearance and physical properties.

[James Catmur]

You would need to look at why they have crystallized differently. Take the example of diamond and graphite and look at how C crystallizes as the temperature and pressure vary -

This discussion might help, but note that it is about how the same mineral can form in many ways, not how the same compound can crystallize in different ways and form different minerals:

https://www.mineral-forum.com/message-board/viewtopic.php?p=78923#78923

[John S. White]

I am not sure that the reference to "why they crystallized differently" is really going to help Paul better understand polymorphs. At least two of the three (or more) titanium dioxide minerals are often found coexisting, that is they are found in the same environment. I think that Alfredo's comments are really all that need be said.

[Paul Biehler]

Thanks to all of you !

Paul