Did you know that the upper mantle of the earth is made out of something that we consider a jewel?
The upper mantle is primarily peridotite, which is named for the gemstone peridot. It is also known as olivine. We know this because some of it has been brought to the surface from depths of 30-200km, which is too deep to mine, by volcanic eruptions. Olivine is the primary mineral in peridotite, and can be many shades of green, depending on the amount of magnesium. Gemstone-quality peridot is pale green. There are a very few "green sand beaches" in the world where the sand is primarily olivine.
When you think of the mantle, you might think "red and molten," but it isn't molten, it's ductile (as opposed to brittle like cold rocks on the surface) and convects very slowly. And, it's mostly green!
So, aside from being a beautiful place, the earth is literally a jewel.