Crazy realistic DRAWING: a MARBLE or glass BALL

Drawing a crazy realistic marble or glass ball (tools listed below). Music by Kirill Khursey please feel free to visit Final picture: Used tools: heavyweight gray paper, 9B, 7B and B pencils (Caran d Ache grafwood), paper stomp, colored pencils (Caran d Ache Supracolor Soft), fibre tip pens (Staedtler Noris Club 320 Double Ended Fibre Tip Pens), markers (Tria Letraset), black