I found something that helps my arthritic thumb

Borax is found in the laundry soap section of the grocery stores. I'm not sure if it's pure borax. I do know it will kill ants when moistened with sugar water.

It is very pure. They do refine it after mining to remove rocks and things and then it is processed to separate it from the salt that is also present. 

If you read up on it when you drink it it reacts with the hydrochloric acid in your stomach which turns it into, sodium chloride, water and elemental boron. Sea salt actually has borax in it because it is water soluble but there is far less of it than sodium chloride. And it kind of makes sense that a person's body would need it just like you need salt as life sprung forth from the ocean. There has been all sorts of research on it and it has shown to benefit bone and teeth health. It also helps prevent calcification of soft tissues. It is a lot of sciency stuff but it makes sense.