  We present a detailed analysis of the prompt and afterglow emission of GRB
050410 and GRB 050412 detected by Swift for which no optical counterpart was
observed. The 15-150 keV energy distribution of the GRB 050410 prompt emission
shows a peak energy at 53 keV. The XRT light curve of this GRB decays as a
power law with a slope of alpha=1.06+/-0.04. The spectrum is well reproduced by
an absorbed power law with a spectral index Gamma_x=2.4+/-0.4 and a low energy
absorption N_H=4(+3;-2)x10^21 cm^(-2) which is higher than the Galactic value.
The 15-150 keV prompt emission in GRB 050412 is modelled with a hard
(Gamma=0.7+/-0.2) power law. The XRT light curve follows a broken power law
with the first slope alpha_1=0.7+/-0.4, the break time T_break=254(-41;+79) s
and the second slope alpha_2=2.8(-0.8;+0.5). The spectrum is fitted by a power
law with spectral index Gamma_x=1.3+/-0.2 which is absorbed at low energies by
the Galactic column. The GRB 050410 afterglow reveals the expected
characteristics of the third component of the canonical Swift light curve.
Conversely, a complex phenomenology was detected in the GRB 050412 because of
the presence of the very early break. The light curve in this case can be
interpreted as being the last peak of the prompt emission. The two bursts
present tight upper limits for the optical emission, however, neither of them
can be clearly classified as dark. For GRB 050410, the suppression of the
optical afterglow could be attributed to a low density interstellar medium
surrounding the burst. For GRB 050412, the evaluation of the darkness is more
difficult due to the ambiguity in the extrapolation of the X-ray afterglow
light curve.
