I have some practical question about Jades

What are they made of? Is it actually like the gemstone?

How big are they supposed to be? Are they tiny - less than 1 cm - or are they more substantial, like an inch or 2 across (especially the 3-cost ones)?

Where/how does Yi equip them? They seem to have metallic sockets and I've suspected Yi's body has some mechanical components due to [Lore Reasons]. Are they placed along the spine or around the heart, or maybe on the hands like rings or the back of the palms?