Sometimes it just looks like a lump of stone, although it may have an interesting colour or pattern. However, sometimes the mineral forms strange shapes. Left is hematite in its botryoidal form. This means it comes in blobs. Another botryoidal mineral is malachite , where the layering of the blobs give its distinctive stripes of different shades of green.
Crystals are the most famous of natural mineral shapes.
Quartz is what most people think of when they say crystal. The crystals have six parallel sides and then, at one end, slope towards a point or a short edge right at the top. All faces are very smooth and shiny. Indeed, it's hard to believe that this is natural. Sometimes quartz crystals are packed together so you don't see the parallel sides, just the point at the top, like this amethyst .