Did explosives exist before the discovery of gun powder? Did the concept of an explosion even exist before the discovery of explosives?

Probably the oldest credited explosives also have Chinese origins. According to Joseph Needham, the custom of exploding bamboo sticks first appears in the written record in the late third century, as a defense against the dark arts:

People cast lengths of bamboo on the fire, which explode and jump out of it, thereby scaring away these [mountain demon-beast-thieves] altogether.

This works because bamboo is a cylinder, with air pockets created by septate fibers. When roasted over a fire, the air heats and explodes. Marco Polo actually recounted this tradition and its impact:

I will tell you how it is that the canes make such a noise. The people cut the green canes, of which there are vast numbers, and set fire to a heap of them at once. After they have been awhile burning they burst asunder, and this makes such a loud report that you might hear it ten miles off. Anyone unused to this noise who should hear it unexpectedly might faint or die of fright...Those who are not used to it stuff their ears well with cotton, and wrap up their heads and faces with all the clothes they can muster until they have become used to the sound. It is the same with horses.

Needham argues that the sound was the major "weapon" here, and that initially, packing gunpowder into tubes was meant to enhance that more "psychological" warfare. (Although he goes on to discuss the rather rapid evolution into various types of projectile and mine explosives for military use. Both East and West had long traditions of incendiary weapon use before gunpowder).

It seems likely that original Greek fire was propelled out of the "tubes" on fire-ships via some sort of explosion as well. Contemporary accounts stress the noise of the initial firing. Alex Roland posits that the tube-shape and the distance needed to...fire the fire...suggest some form of explosion as well.

I've also seen references in secondary literature to explosions in medieval coal mines and to ancient Roman fireworks (ETA: see my comment here) of some sort in the fourth century, but the scholars aren't citing primary sources. (I understand that Dampf plus candles is a danger in relatively-enclosed coal mines; I just want documentation of something resembling an explosion because of it instead of just miners getting woozy). So if anyone turns those up, that would be great!