Hey there! First of all, I love your art! You're a huge inspiration to me. Sorry if this is bothering but what Gem would be suitable for a Rose/Sapphire fusion? Like, a gem that has a combination of their Crystal constructs and a gem that can come in different colors?
Well I chose Druzy Quartz for that fusion (haven’t drawn them properly yet) cause they often come in purples but they also come in all different colours
But for you if you’re not wanting to stick with the “all Rose Quartz fusions make another Quartz” theory I’m kind of rolling with I’d say to pick a mineral type that yeah, has a few colour varieties and go from there, maybe Zoisites? There’s Tanzanite (which in itself comes in quite a few colours, purple, blue, orange, pink) also Thulite comes in shades from pale pink to red