In the movie Noah, which puts a new spin on the old legend of Noah's Ark, In the movie Cain's descendants mine a ore called Zohar. For those of you that have yet to see the movie, first go watch it! But if you don't have time zohar is a bright gold colored object that, when kinetic energy is applied to, bursts into flame in a fashion similar to thermite. Is it possible for ore like this to exist in the natural world? If not how close can I get?
It is remarkably hard for an ore to exist like that. To do what you describe requires a high level of chemical energy bundled up with an activation energy required to make it activate. However, you won't find it in the ground. Activation energy is a statistical thing. Eventually random molecular movement is enough to achieve the activation energy required, setting off a little bit of the ore. On the scale of millions of years, the ore would lose its power.
Nitrogen tri-iodide is an example of an explosive that does exist which is set off by the lightest touch. However, these compounds are constructed by human intevention and have a shelf life. The shelf life may be measured in years, but typically not millions of years.
A few options which could make it plausible:
- Young earth: if the earth is very young (<10,000 years), it may not have had time to react all of the Zohar, so there may still be some that is minable.
- Sensitive to air: many explosive compounds are inert when mixed with water, but become explosive once they dry. You might be able to work the chemistry such that the rock is a mix of Zohar and some inhibitor which keeps Zohar from going off. If the inhibitor reacts to the oxygen of the air, you could keep the Zohar from going off until after the oxygen has done its trick. Zohar might need to "age" in open air a few weeks to make sure all of the inhibitor is reacted before you strike it.
- Lord's Luck: If you've got the ruler of the universe watching over you, they can do what they like =)