I found these cool marble tile pieces at H.D. and etched them today using varying speeds and power. No matter the power/speed settings or number of passes, it only took off the very top layer, roughly 1/100th.
How would I go about getting a deeper etching?
As you’ve already discovered, you can’t. The laser doesn’t have the power to do more than mark the surface of many materials.
Happy birthday @eflyguy. 
yea, what he said! ^ Happy Birthday 
If you blast hard enough you will turn calcium carbonate into calcium oxide where it will suck out whatever humidity is about and turn into quicklime,
