When magma<span> cools, </span>crystals<span> form because the solution is super-saturated with respect to some </span>minerals<span>. If the </span>magma<span> cools quickly, the </span>crystals<span> do not have much time to form, so they are very small. If the </span>magma<span> cools slowly, then the </span>crystals<span> have enough time to grow and become large.</span>
