/usr/share/gwyddion/glmaterials/Black-Plastic is in gwyddion-common 2.47-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 | Gwyddion resource GwyGLMaterial
0.0 0.0 0.0 1.0
0.01 0.01 0.01 1.0
0.50 0.50 0.50 1.0
0.0 0.0 0.0 1.0
.25
|