Vintage 1990s Signed Sterling Earrings with Opal and Gemstone Style Stones

Sterling silver dangle earrings - these are signed, and the sterling is marked. They were sold to my mother in the 90s new as opal and genuine gemstone earrings - and I’ve seen the same vintage earrings being sold elsewhere online as genuine opal and gemstone - but looking more closely at it, the stone looks to me like it may be glass. If the stone is glass, the opal may be simulated too. Beautiful regardless, but I’m unsure what the components are besides the sterling. Marked 925 and the makers mark is MF with a copyright symbol.