Why some minerals form as seemingly perfect cubes?

Question

While visiting Harvard’s natural history museum on a trip to Boston, i’ve seen some minerals (or crystals. Not exactly sure of the difference between them) that seems to have naturally formed into near perfect cubes. How is that possible?
It seemed to be most frequent in pyrite.

Thanks in advance!

(Tagged as chemistry, but not sure if it fits)

In: Chemistry

Answer 1

Every crystal has a ‘shape’ (though some have more than 1, which can mix things up). This is the combination of the angles that the crystal’s molecules form with each other. Some common shapes are hexagons (like ice), or cubic (like pyrite). A decent list of them is on the [crystal system wikipage](https://en.wikipedia.org/wiki/Crystal_system), which is also a good place for further reading on the topic.