chemistry in fiction - Which crystals can exist permanently (and do not break down) under normal earth like outside conditions?

Hi I am looking for crystals I can use in the world of my novel but I have no idea what types to use or what there are.

So my question is what kind of crystals fit these criteria:

• They must be able to exist “permanently” without breaking down in normal earth conditions/atmosphere.


• They must be able to grow quite large. (I’m thinking about large hexagonal crystal columns)

I would be very happy if you could list any crystals you know that fist the criteria. With the name I should be able to research further myself and narrow it down. Thanks in advance.

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P.s. some of you might have some feeling of déjà vu reading my question as I asked a similar question before but that one was marked as to brought so I am asking it again but trimmed down. link: How do i create a significantly correct world with large crystal formations in my novel?

P.p.s. if this question is to brought as well please leave a comment explaining how I can make it better because I otherwise really have no idea how to fix it.

Answer

Quartz (silicon dioxide) sounds like a good bet. It is inert, safe to be around, and insoluble in water. Some examples of naturally occurring quartz crystals are really huge - visit the National Museum of Natural History if you are near DC - or any other natural history museum near you. There you will likely see many other naturally occurring minerals of defined chemical composition that form large crystals. Or go online and look for pictures.