Over the holiday's I gathered a few stones from my beach visits to have a go at making them into buttons.
They will need to be fairly flat and not to big. There are soft rocks and hard rocks - sand and lime stone are the easiest to drill. Some of the ones I collected where too hard for these cheap drill bits.
Also take into account the size of the stone. The bigger they are, the heavier they are and they will not be useful.
I purchased two different types of drill bits from the local hardware store.
You can go all out and purchase proper drilling bits more suitable but they will cost a lot more. But these were cheap and a good place to start.
The 3mm bit was designed for masonry such as bricks, tiles and concrete.
The 1.5mm was a Hi Power Bit to be used for metal, wood & plastic.
Mark where you would like the holes to be.
Add a piece of wood under the stone to protect the surface top you are working on.
Hold the stone in a Multi Grips or an adjustable plier to keep it still.
Some suggest working in water but I found it awkward to hold the stone flat with the grips and drill in the water.
You may wish to protect your eyes with glasses.
Carefully drill your holes.
Surprisingly, the larger 3mm masonry bit didn't really work. It blew out the back and the front hole entries were also messy. The drill was set to hammer.
The 1.5mm bit was easier to use and gave a much cleaner hole.
So overall for a first up attempt it was an OK result, I think purchasing more suited drill bits are the answer.