The figure is certainly carved from a medium grained pinkish granite. Most Cornubian granites, but not all, are white.
Describing the lithology as micro-crystalline and a slowly cooled volcanic would be thought bizarre if we did not know it was a joke -the hint is that the term batholoith was used- showing the depth of his whimsy.
I suspect the phyllosilicate to be muscovite rather than biotite.
Dating the grnite would be the obvious but expensive way of determining if it be Cornubian or far older and therefore more likely to be continental.