How do crystals form and how do they grow?
Crystals start growing be a process called “nucleation”. Nucleation can either start with the molecules themselves (we’ll call this unassisted nucleation), or with the help of some solid matter already in the solution (we’ll call this assisted nucleation). I’ll write about both. Before I do that, here is a general explanation from Tony Linden: Once a solution is saturated, or a melt nears the solidification point, solid material starts to form. If the molecules come together in a random arrangement, they do not occupy the closest packed space. However, if the molecules come together in an ordered array, they pack together in a much smaller space, like in a properly assembled jigsaw puzzle (see how much more space an unassembled puzzle occupies when the pieces are randomly positioned to touch each other, but not overlap). Thus, the proper packing uses less space and is also of lowest energy, which is always the most stable condition. As it happens, this ordered array pattern repeats its
