Silicon-Germanium　in　a　hexagonal　crystal-structure　is　a　candidate　material　for　a　direct　band-gap　group　IV　semiconductor　that　can　be　integrated　into　the　CMOS　process.　It　has　recently　been　synthesized　as　a　crystalline　shell　grown　epitaxial　around　a　nanowire　core　of　hexagonal　Gallium-Phosphide.　In　order　to　study　the　optical　properties　of　this　newly　generated　material　and　evaluate　its　potential　for　building　optical　devices　it　is　necessary　to　grow　defect　and　impurity　free　hexagonal　Silicon-Germanium.　Impurity　detection　and　mapping　in　nano-structures　is　however　challenging　as　most　bulk　and　thin　film　characterization　methods　cannot　be　used.　Here　we　show　that　Atom　Probe　Tomography　can　be　used　to　map　the　impurities　in　hexagonal　shells　of　Silicon-Germanium　and　Silicon.　This　will　allow　to　optimize　growth　of　hexagonal　Silicon-Germanium　nanocrystals　towards　impurity　free,　optically　active　crystals.