/usr/share/gwyddion/glmaterials/Copper is in gwyddion-common 2.50-2.
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
0.19125 0.0735 0.0225 1.0
0.7038 0.27048 0.0828 1.0
0.256777 0.137622 0.086014 1.0
0.0 0.0 0.0 1.0
0.1
|