Atium crystals and allomancy

[+Krox]

I'm re-reading Mistborn and got to the part where Kelsier ruins (pun intended) the Pits of Hathsin, and I was wondering if we know why the crystals break from the effect of allomancy?

I've googled and searched and thrawled WoBs but can't seem to find what I'm looking for, because most old theories I find suggest that it doesn't break from all kinds just when pushed/pulled by steel/iron. This is supposedly also why Mare could be sent to the pits (with or without being spiked first, but lets just say she isn't).
My problem with this is that as soon as Kelsier burns Tin he hears a crystal crack!

Quote

He stepped over to the rift and forced gimsself to climb donwn inside of it. Then he burned tin. Immediately, he heard a cracking sound from below.

I'm not bothered with Mare being sent to the Pits with all the fuss she could destroy it, she'd maybe get the slightest amount of tin through traces in food or water but would be killed the first week she didn't supply a geode and thus problem solved for the Ventures/TLR...

So, educate me!

Edit: Also, why do they break from allomancy?

Edited October 19, 2020 by Krox
Edit: extra question

[+Bzhydack]

We dont know (noone asks Brandon, or I didnt fuond it), but i think this is the same reason why mists were push out from hemalurgicly spiked person - they were Connected to opposite powers.

[+Krox]

13 minutes ago, Bzhydack said:

We dont know (noone asks Brandon, or I didnt fuond it), but i think this is the same reason why mists were push out from hemalurgicly spiked person - they were Connected to opposite powers.

I agree on the assesment of Ruins investiture reacting to the presence of Preservations Investiture, it makes much sense. This is what I have concluded myself. Wonder if somebody knows better..!