A.L. Sprague. DB. Nash, R.C. Witteborn, D.P. Cruikshank
(Adv.Space Res., 19(10), pp.1507-1510, 1997)
Mid-infrared (7.5 - 13.5 \mic) spectra of Mercury
at two equatorial longitudes obtained at the
Infrared Telescope Facility (IRTF) at Mauna Kea Hawaii
show spectral features indicative of plagioclase feldspar.
Spectra resembling that of powdered labradorite (\lab)
were obtained near 120 degrees mercurian longitude.
Spectra from a second region near ~ 30 degrees longitude.
longitude resemble laboratory spectra from a lunar breccia made up
of primarily plagioclase (probably anorthite)
and pyroxene fragments. Abundant feldspars of varying compositions
on Mercury's surface indicate that the surface is heterogeneous and
that the planet is highly differentiated.