Mineral that explodes when cooling down

While playing old games, I encountered a friend I knew from SciFi series and games alike, the Merculite missile. While thinking about what Merculite might actually be (and linking it to a mineral from the planet Mercury in my head), I had a basic idea for a short story about a freighter transporting a mineral that is not dangerous while hot (but still non-liquid), but get dangerously explosive if its temperature drops below a certain point.

This might not work out at all and does not necessarily require hard science, but I was wondering if there are any known components or minerals that exhibit such behaviour.

My basic school and university chemistry tells me that it is counter-intuitive as any exothermic reaction starting once the temperature drops below a certain point would heat up the mass again, but maybe there are some weird chemical or physical things that may allow for this, like

1. It really simply explodes once the temperature drops too low or
2. it is only stable above a certain temperature and thus seperates itself into two or more components that form an explosive liquid that explodes once it reaches a critical mass or
3. I have absolutely no idea.

Are there any weird substances with such or similar attributes, are such substances even possible with our current understanding of physics and chemistry or would I need to use a pseudoscience mineral?

UPDATE Wow! I'm really impressed and thankful. Please give me some time to pick the answer - I'm not sure if I should pick the one that I like best, but that goes a little bit in a different direction than my original question, or pick the one that answers my original question best.

posted over 7 years ago

Blutkoete‭

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