The incredibly famous Prelude No. 1 in C Major by J.S. Bach is possibly one of the most popular pieces performed on marimba due to its beautiful simplicity and endless arpeggiated passages. 
 
Originally written for piano in 1722, I have arranged this for a four octave marimba and added suggestions for the harmony above in chord symbols to help the student understand what they may be playing. Of course, if you'd prefer a version without the chord symbols and arranged for a 5-octave marimba (which would probably sound better, once you get below the C in bass clef), then don't hesitate to ask!