Does anyone know what a Sunstone is? It's mentioned in the PHB as the material component for a Sunburst spell, and the UA stuff in the SRD mentions it likewise as a metamagic component for same spell. But it never turns up anywhere else that I can find. So what the heck is it? I've seen a reference to a variant of feldspar called 'sunstone' that can be considered a minor gemstone, but somehow that doesn't quite fit... or is that it?