Laser engraving stone slabs or rocks with a polished texture or very smooth surface will provide the best results. To achieve the most desirable engraving result possible, place the stone on a stone processing equipment  to ensure that the finished product is not distorted by curves.
Natural stones with a round surface can still be laser engraved, just simply place the object on a horizontal plane. We also recommend using a support to assist with this process, such as modeling clay. When focusing the laser beam, you will want the engraving to be as uniform as possible, so input an average value of the engraving area for the best results.
Stones can be purchased from a variety of resellers and we have found that the tile departments of hardware stores typically have an excellent selection of stones for jewelry, worry stones and more. You can usually find all kinds of unique stones to choose from, including mosaic tiles composed of leveled river pebbles and even marble stones in a variety of colors. We recommend soaking the mat in warm soapy water to dissolve the glued backing that holds the stones together, and in doing so, you then have lots of smaller stones ready for laser processing at a fraction of the cost!
Depending on the type of stone being laser engraved, most will produce dust that will typically stick and cause stringing. Therefore, before each engraving job (and even during longer engraving jobs) make sure to check the nozzle opening, as it can become clogged from stone dust and obstruct the laser beam path. System performance can be restored on your laser by simply wiping the nozzle with a cloth or rinsing it with water, as well as by verifying lens and mirror functionality at intervals during the stone engraving process.
We also recommend cleaning the stone prior to laser engraving it, if you want to remove any natural dirt and debris that the stone may carry. Rinsing the material post-laser engraving will wash away any resulting stone dust, but cleaning the stone before and after laser processing will provide you with the best possible contrast.