I think this idea is awesome. It is a beautiful way to remember your travels The different colors of sand are so beautiful and varied. You can also collect pebbles and rocks. I also like the idea of writing on the rocks. Here are a bunch of examples.
What I’d really like to do is collect rocks and/or dirt from different places in my family’s history. Wouldn’t it be cool to go back to England where my great-great grandma, Mary Taylor was born and collect some soil. Then trace her journey to the west, stopping at key points along the way to collect more sample. Layered in a jar with labels of some kind and maybe a mini book to explain the importance of each place. With the power of the internet it would probably be possible to find people who live in each of those areas to gather what I’d need and ship them to me. The trip would be more fun but it isn’t in my budget in the near future.