  Modeling extinction along anomalous/non-CCM sightlines, which are
characterized by a broad $217.5 nm$ bump and steep far-ultraviolet (FUV) rise,
is reported. The extinction along these sightlines, viz. {HD 210121}, {HD
204827}, {HD 29647} and {HD 62542}, is difficult to reproduce using standard
silicate and graphite grains. Very good match with the observed extinction is
obtained by considering nanodiamond component as part of carbonaceous matter.
Most of these sightlines are rich in carbon and are invariably backed by a
young hot stellar object. Nanodiamond is taken as core within amorphous carbon
and graphite. These core-mantle particles taken as additional components along
with graphite and silicates lead to reduction in the silicate requirement. The
abundance of carbonaceous matter is not affected as a very small fraction of
nanodiamond is required. Extinction along sightlines that show steep FUV is
also reported demonstrating the importance of nanodiamond component in all such
regions.
