type of jade, rare, valuable
瑋 centers on a rare and valuable type of jade, emphasizing preciousness and scarcity.
瑋 combines 王 (jade) with 韋, which likely contributes the sound and possibly the idea of something wrapped or precious. The exact historical development is uncertain.
The left side 王 (jade) tells you it's a precious stone, and the right side 韋 looks like a wrapped treasure. Imagine a rare, valuable jade wrapped carefully to protect it.
For イ, picture an eagle (イーグル) guarding a rare jade: eagle -> イ, and the precious stone is kept safe.