inferior agate
玞 refers to a type of inferior or low-quality agate, a gemstone considered less valuable than true agate.
玞 combines 王 (jade/gem) with 夫, which likely serves as a phonetic component. The character specifically denotes a lesser type of agate.
The left side 王 (jade) tells you it's a gemstone, and the right side 夫 (man) hints that it's a 'lesser man' among gems—an inferior agate.
For フ, imagine a jeweler saying 'Foo!' in disappointment when they realize the agate is inferior: Foo -> フ.