Raise the bar and use diamond.

I used to be in the CVD diamond world. On my honeymoon nearly 30 years ago, my wife and I were hiking in the Himalayas, in Sikkim.

My Dad loved diamonds and used them in his work (geophysical drilling, using diamond bits). He passed a year before my marriage. I wanted to leave a rem meminisse eum a in his honor.

So I grew a 2mm thick x 2.5cm diameter diamond disc. I used some nucleation art to make his first name appear as a texture variation in the faceted growth surface. I left it on a protected ledge at ~ 19,000 feet, with a note that just said “Thanks, Dad”.

That disc, or its fragments, will be around until that mountain gets covered by a lava flow or subducted into the mantle.

Concrete? A thousand years? Let's aim higher. :-)