dig-now drops wrong boulders

[Ankwelth]

Using DF 53.02 and DFHack, the dig-now command creates boulders of the wrong material.
Digging Dacite wall with the dig-now command leaves Sandstone boulders, and Granites gives Claystone boulders.
Alunite and Microcline seems fine though.

[quietust]

The dig-now plugin uses MapCache's baseMaterialAt() to determine the material of layer stone tiles, so it's possible there's a general fault there.