jewel
瑾 centers on a precious jewel or gem, often with a connotation of fine quality or purity.
瑾 combines 王 (jade/jewel) with 堇, which likely contributes the sound キン and may carry a sense of fine quality. The exact historical development of 堇 is uncertain.
The left side 王 represents a jewel or jade. The right side 堇 looks like a detailed ornament. Imagine a finely carved gemstone with intricate patterns: 瑾 is a precious jewel.
For キン, picture a king holding a jewel: king -> キン, and the jewel 瑾 shines in his hand.