You could do some OG lithography (the litho in lithography means “stone”) by masking the white or block parts of the QR code and painting on an etchant. I don’t know what the best etchants for stone are, but I imagine HF-containing glass etch would do the trick. (Be very, very careful with HF.)
Instead of making the QR code point to something, you could encode the information directly. A short blurb about a person would fit.
You could do some OG lithography (the litho in lithography means “stone”) by masking the white or block parts of the QR code and painting on an etchant. I don’t know what the best etchants for stone are, but I imagine HF-containing glass etch would do the trick. (Be very, very careful with HF.)
Instead of making the QR code point to something, you could encode the information directly. A short blurb about a person would fit.
You can laser etch/temper stainless steel to put a QR code that’d last longer than any QR code would be practical.
Heating stainless to different temperatures will make it change color enough to make a QR code.