Pseudomorps 					
Egypt, White desert

Very unusual shapes of Fe-containing minerals could be found in White desert in Egypt (near Farafra oasis).
They are pseudomorphs of hematite and limonite after pyrite and markazite. Excellent cubes and stars and other. 
Sometimes you can see even more stages of material exchange: some shells or petrifyed wood shapes could be found - 
here the calcite or wood as the initial substance.