When I was a kid I took a 12" by 12" Freznel lens and melted the surface of several stones. The pic is of one I was comissioned to make. Not a laser but a very high concentration of light, around 2000 F on good stones. The rock would melt into bubbling black glass.
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Cool i just aquired a large fresnel lense i didnt know i could do stuff like this with it. The melted sections looks like the rock @dan put in the glowforge Whatever happened with the engraved rock?
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Thanks! That is what reminded me of my work was the rock that @dan did. Please wear high brightness eye protection! I also once in an instant cooked a point on my finger one time to well done 
You will find that rocks range from working well to not working at all to flaking off after you have worked on it for an hour! :-/ I also found that it melted glass dust into little balls. It will also melt bricks and concrete.
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Wow, this opens a whole new range of ideas. Again, this is creative overload. I should have ordered 5 Pros to handle all the ideas.
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As a senior in HS my boss’s dad wanted me to go the University of Minnesota where we was a mechanical engineering professor. Part of the informal tour was to show me a solar collector about six feet in diameter made up of hundreds of individual mirrors all focused on a single point. At that point was an inch thick piece of plate steel with a golf ball size hole melted in it. I didn’t get to see it in action, but that plate of steel made an impression. The kerf was a bit larger than your typical laser cutter, but for those who want to cut metal…
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Out of curiosity, gernreich, were you living in a particularly sunny part of the world when you did this project? I am guessing that this wasn’t done in Ottawa in February…
Good point when picking eye protection. It’s not just about the laser, but also about what is being burned.
Is this sand stone?
@hroger1030 , I did most of the work in southern Arizona on VERY clear days. I found however that I was able to do the same work at the US/Canada border if the day was VERY clear.
@soldiercoleman I would call it “lava rock” that has bleached over a very long time in the desert.
Now THAT is power concentration!!!
I’m in the Southwest. I bet petrified wood could give an amazing look also!
Holy smokes!
What I had to do was test each type of stone I could get a hold of and see if it worked. I don’t think I ever tried petrified wood because at the time I did not have any, since then I found plenty of other stones that worked so I never have tried it.
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I picked up smooth stones along the lake bed today after seeing this posting. They are not very large, but big enough to place a design. I am in Missouri so I am assuming it is limestone. Very light but smooth, probably from the water. Has anyone had any experience working with limestone?
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The stones that worked for me were silicates. Ones that melted into glass in other words. I have not worked with limestone.