8 upvotes, 1 direct replies (showing 1)
View submission: Why does quartz come in so many different shapes and colors?
Chemical compatibility and ionic radius are pretty closely linked. In fact, a lot of cation substitutions involve species that have a different charge from the one they're replacing. (This is why some clay minerals frequently have a permanent charge.) For various reasons, approximating the right size (or the right lattice shape) is often more important for chemical compatibility than having the charges all add up to zero. The changes in lattice spacing from ionic substitution are *usually* fairly small; it's just that small changes in internuclear distance can be significant relative to the wavelengths of visible light. That, in turn, changes the extent to which different colors of light are absorbed and transmitted through the volume of the sample.
Comment by opteryx5 at 26/02/2022 at 22:58 UTC
3 upvotes, 1 direct replies
Ahh I see. I guess that makes sense from an impurities perspective, because the impurity really isn’t constitutively a part of the quartz itself? (i.e., it’s not going to be chemically bonded to either the silicon or the oxygen) So I guess size of the ion becomes the main consideration, and if it fits, then it’s compatible. (If that makes sense. I think I’m understanding you.)