We propose to develop LUNA, a compact and lightweight X-Ray Diffraction (XRD) / X-Ray Fluorescence (XRF) instrument for mineralogical analysis of regolith, rock samples and dust, in lunar surface exploration. LUNA is based from the concept of CheMin, the XRD/XRF instrument of MSL, but is redesigned to provide a more compact unit at much reduced costs. Many details of LUNA derive from the designs of a small portable XRD/XRF instruments developed and marketed by inXitu. Bringing LUNA to TRL 6-7 is possible within the scope of this Phase II because key components have been or are being developed. Phase 2 addresses the missing critical subsystems: a low-cost flight-qualifiable X-ray CCD, and flight-qualifiable electronics to drive the detector and control the instrument. LUNA is not frozen in a particular geometry or mechanical implementation, it is meant to be flexible to answer the specific needs of any lunar mission. Transmission or reflection geometries are possible as demonstrated by inXitu's commercial instruments. Phase 2 will demonstrate a reflection version of LUNA operating under vacuum. This work leverages on the extensive experience of the PI and the company with XRD-XRF instrumentation in terrestrial and planetary applications.