Almost every solid that occurs in nature is made up of crystals. The minerals found on earth have differently shaped crystals.
Salt looks like rough sand to the unaided eye.
However, when viewed through a magnifying glass or a microscope, it is actually made up of tiny cube-shaped crystals. Some crystals, like salt are very small, while others are large enough to be seen without a hand lens or a microscope. Some crystals are formed when molten rock cools and hardens. Others are formed when water containing dissolved minerals evaporates. In both cases, the atoms of the minerals form solids by coming together in regular repeating patterns.