The bane of many photographers is camera shake. Even if you think you are holding it steady, you may not be.
So for photographing minerals, it pays to use a tripod. Even then, you can experience shaking through an uneven/unstable floor (eg: old timber floorboards), the action of the mirror inside the camera, or simply moving the camera when pressing the button. Long exposures compound the problem.
If your camera has the option of connecting a bulb, or simply a timer, use it. Most of my photos are taken via my PC. This helps a lot too.