  We have used different spectroscopic techniques to obtain a consistent
quantitative absorption spectrum of a sample of meteoritic nano-diamonds in the
wavelength range from the vacuum ultraviolet (0.12 $\mu$m) to the far infrared
(100 $\mu$m). The nano-diamonds have been isolated by a chemical treatment from
the Allende meteorite (Braatz et al.2000). Electron energy loss spectroscopy
(EELS) extends the optical measurements to higher energies and allows the
derivation of the optical constants (n & k) by Kramers-Kronig analysis. The
results can be used to restrain observations and to improve current models of
the environment where the nano-diamonds are expected to have formed. We also
show that the amount of nano-diamond which can be present in space is higher
than previously estimated by Lewis et al. (1989).
