Middelheim Museum

Middelheim museum in Antwerp houses an extended collection of the 20th century sculpture. I was curious how many concrete pieces they have. There were some objects that looked like concrete but when I came closer and touched them and scratched them gently with my nail, and knocked lightly with my knuckles, they turned out to be metal or natural stone. I managed to identify only four (!) concrete pieces and was absolutely sure but 2 out of four were 'granite stone' according to internet catalogue. Couldn't believe my eyes. Granite stone 'Column pavilions' by Charles Vandenhove