It is the result of an earlier commit that merged down artifact definitions. Resolved by changing the name of the diamond face to 'diamond' over 'gem'.
Patch https://sourceforge.net/p/crossfire/patches/367/ by tituss, picture by Saiapatsu.
git-svn-id: svn+ssh://svn.code.sf.net/p/crossfire/code/arch/trunk@21109 282e977c-c81d-0410-88c4-b93c2d0d6712