19, feldspar; 20, crystal of galena, showing the cube and octahedron 

 combined, also seen in tigure 3; 21, galena, showing cubic cleavage; 

 22, sphalerite; 23, garnet (dodecahedron); 24, pyrite (note the striations 

 on the cube faces. See figure 2.) (About two-thirds natural size.) 



320 



