How do i create a significantly correct world with large crystal formations in my novel? I have uploaded an shorter and less broad Question which is largely the same but requires a different kind of answer. What i want to say is that i re-asked my question in a different way because i do not want to delete the answers i got  here so far and because the answered also would be incorrect in the context of my re-asked and re-written question
link: Which crystals can exist permanently (and do not break down) under normal earth like outside conditions?

Hi I am not really all that well versed in chemistry or molecules for that matter but I am trying to find a way to "create" a scientific and realistic (trough probably unlikely) world with large crystal formations on the surface. The reason I want this is because I want to create a species for my novel that has its culture based around the large crystal formations living on the planet.

Now to limit my question a bit I would like the answer to these two points:


What kind of crystal(s).
How do you think the process should work.
What limitations it creates.


The criteria are that:


The crystals must be permanent without breaking down in normal earth conditions/atmosphere.
Preferably no interference required by intelligent lifeforms.
There will be oxygen and carbon dioxide in the atmosphere.
They must be able to grow quite large. I’m thinking about large hexagonal crystal columns.


What are the tools?:

Well you can more or less use anything in nature, you can make suns explode if need be. But a more probable start would be selecting the chemical composition and what would be needed to form crystals from that point.

For instance if you need a long period of very high heat and then cooling down to “normal” temperatures you can make the system sun go red giant and heating the planet before becoming a white dwarf.
Do you mind a scenario somewhat less dramatic than exploding suns? ;)


Just let selenite ($\ce{CaSO4*2H2O}$) cristallize very slowly und undisturbed in a system of caves for a long time. 
Let the inhabitants of your world discover the cave system or let parts of the cave system collape to make it more accessible.


A model for this already exists: the Cave of the Crystals, connected to the Naica mine in Mexico.



Update

Note that I'm not a geoscientist, but to me, large hexagonal columns that can exist under earth's atmosphere cry basalt, which in turn indicates vulcanic activities.

The English wikipedia has a list columnar structures resulting from vulcanism. Some examples are


Giant's Causeway in Northern Ireland
Fingal's Cave in Scotland
Devil's Postpile in California