Book 27, Question 14
Why do some crystals grow as needles and others as cubes?
The shape of a crystal depends on its internal lattice and on where it grows.
Some faces grow faster than others, which stretches the crystal into needles, plates, or blocks. Temperature, space, and the other chemicals around the crystal all matter. That is why the same mineral can look different in different places, and why experts also test hardness and color before naming it.