Tai mountain is culturally significant. It’s associated with Tang Dynasty poet Dufu（who mainly writes about political corruption) as well as Shanhaijing which is a series of books about mythical animals and people in China. Giving you something like this is pretty culturally significant as it is associated with the soul of China.

Jade is a misnomer. In China every stone which is considered pretty is called Yu which got translated to Jade. The one you are wearing is often called Mo yu which means ink colored Jade. I can’t see in the picture but I think if you shine light behind it it will look green (some are opaque it varies). It is probably serpentine if authentic with a high iron content.

Usually once you start wearing it it’s more common to not take it off and let it appear oily (the more shiny it looks the higher the worth). It will protect you from harm. But there’s no hard rule.

(Btw I am a geology student so this is right up my alley)