The sinuous texture on the outside reminds me of silk.
Still much better then any rock I can produce, but I feel like something is off here. Maybe to much or to strong grey tones? Maybe the background? I can't really tell but I think your previous rocks looked more realistic.
Moonstone is tricky because it's usually very milky/grey, and the blue/green shines are often under the surface, or very subtle. Thanks though! They're great practice, and I'm working on more!