I made a set of 6 coasters, engraved on some old,ugly granite tiles I found in a junk store.
I purchased a bottle of black concrete stain and mixed a table spoon with warm water. Because granite is porris, it allowed the stain to take. I also sanded off the original glossy finish. I allowed it to dry for about 45 minutes. The then used an old rag and started buffing ther center, leaving the edges dark. The old colors came through gold,brown, all kinds of cool shades. The dye is messy but can clean up with water. I suggest only buffing off what you want. It is possible to buff off 90% if your not careful. I then allowed it 24 hours to cure before engraving.
I love working with leather and Xtool has taken it to another level for me. I bought a $6.00 bag of scraps at Hobby Lobby. I took each tile and traced it onto the leather, cut it out by hand, and using epoxy glue, I glued them on. I suggest using a small roller to make sure it goes on even. Once it dried, I had designed a logo of my friends last name. I then used the 20watt head and let my D1 Pro do it's thang!
I found free images online of Angel statues. I wanted them to be weathered and old. Using creative space, I played with the images by inverting them because I would be burning on a dark or black surface. Once inverted,I got rid of a lot of the white spaces. The granite tile had large pores and crevices so it would look like old roman or Greek style.
I always alight from the center. I set the speed at 100, power at 100, and about 200 on the engrave distance. Similar to steel.It's slow, but you need it to etch the granite.
Once engraved you need the final step which is Polyurethane. All of the bright white fresh engravement will instantly turn brownish from the poly. This is one time when the browning effect is desired.