> the use of rope or string, sand, and water to finely cut stones and gems

I haven't heard this one before, that's a great idea. Here's a YouTube video of somebody doing this with jade if anybody is curious:

https://m.youtube.com/watch?v=w_9MCNgY2Ww

This is neat but I could have done without the poor diction, AI voice, and inaccessible subtitles.