A jade bangle is cut from a solid block with a hollow drill, then ground and polished for hours until it is round and even. Nephrite is a calcium magnesium silicate with an interlocking fibrous structure; that interlock is why a thin bangle survives at all, and why jade can be carved so finely.
The colour here is the green-to-grey range that natural nephrite covers. Any internal veining or clouding visible in the stone is characteristic of the material rather than a defect, and it is how you tell a natural piece from a treated one. Fit matters: measure the widest part of the hand, not the wrist, since the bangle has to pass over the knuckles.