Marble and granite engrave like slate, by flaking off a thin surface layer. On dark polished stone the result is a bright, very durable white — the technique used for memorial plaques.
Settings: what really matters
Stone is never laser-cut. When engraving, the stone's own contrast decides the result: polished black granite gives a brilliant white, veined white marble gives weak and often disappointing contrast.
High power, fast speed, a single pass. A second pass re-burns the dust and greys the white you achieved.
Polished stone gives far more contrast than raw or honed stone: the engraved white cuts against the gloss.
Risks and finishing
No toxic fumes, but very fine mineral dust not to be breathed: extraction on, and wipe with a damp cloth rather than an air gun.
A heavy slab will not move, but check flatness: on a slightly domed slab, contrast varies from edge to edge.
To strengthen text, black wax or paint applied then wiped flat fills the recesses and improves legibility further.
Every figure on LaserSettings comes with the machine, the laser source, the material and the thickness it was tested on. A setting published for a 10 W diode says nothing about a 40 W CO2, and a setting for 3 mm says nothing about 6 mm: check those four things before you copy any number.
Settings are confirmed or disputed by the members who reproduce them, so reliability comes from cross-checking rather than popularity. Photos of the result — cut edges, engraving shades, scorching — tell you more than a single number found on a forum.
Whatever the material, treat a published setting as a starting point: run a small power/speed test grid on an offcut, clean the lens, redo the focus, work with fume extraction and air assist, wear glasses rated for your wavelength and never leave the machine unattended.