The Tomuro stones are a type of andesite, so they are not very resistant compared to granite, however they were appreciated because of their unusual colors, with tints of red and blue. Combined, they give a very pleasant look, as you can see in this photo of the Kanazawa castle...
EXIF info:
Nikon Df
Lens: 14mm F/2.8D
Focal Length: 14mm
Aperture: F/7.1
Shutter Speed: 1/320s
ISO Sensitivity: ISO 400