laser etching attempt on sand stone

ran laser over sand stone to etch and apparently instead vitrified it together because on scrubbing I ended up with slightly raised areas where the laser had traced rather than it being indented there, (did this before and it worked but each stone type is different so...) this stone seemed to have a lot of metal oxide in it making it particularly orange and red as opposed to other more yellow sand stone or the black and or dark brown sand stone, all of which absorb the laser (blue laser) but some absorb it better and ablate better than others. Will have to try again maybe with the settings as they are used for engraving into steel