Material you need.
A rock with a dark color so the etch will have contrasting letters.
Access to a laser etcher.
I made this at TechShop. www.techshop.ws
Step 1: Create Your Design File
Step 2: Setup the Laser Bay.
I used a straight edge and the calipers to get this as close as possible when entering the material thickness in the printing preference.
I turned the rock over and made some test passes to besure I had the distance right.