Middle: compositions (wt.%; Table 2) of Apollo samples on a ternary diagram, with their Off/On-band albedo ratios indicated by color, corresponding to the axis at the bottom. Left/right: FUV spectra of various terrestrial endmembers further demonstrating the sensitivity of the FUV to increased felspathic content. Spectra are adapted from Hapke et al. (1978), Wagner et al. (1987), and Philipp (1966). The arrow indicates a general trend of LAMP Off/On-band ratio increasing with plagioclase content.