Answer. Because when magma cools, crystals form because the solution is super-saturated with respect to some minerals. If the magma cools quickly, the crystals do not have much time to form, so they are very small. If the magma cools slowly, then the crystal shave enough time to grow and become large. :)
Explanation: I Hope this works! Have you tried the magic crystals It is so cool you get to see it grown. But you have to put the things in the contanier. FUN PART IS, YOU GET TO SEE IT GROW! :)))
