  We have studied the interstellar extinction in a field of 3' x 3' located
about 6' SW of 30 Doradus in the Large Magellanic Cloud (LMC). Hubble Space
Telescope observations in the U, B, V, I and Halpha bands reveal patchy
extinction in this field. The colour-magnitude diagram (CMD) shows an elongated
stellar sequence, almost parallel to the main sequence (MS), which is in
reality made up of stars of the red giant clump (RC) spread across the CMD by
the uneven levels of extinction in this region. Since these objects are all at
the same distance from us and share very similar physical properties, we can
derive quantitatively both the extinction law in the range 3000 - 8000 Angstrom
and the absolute extinction towards about 100 objects, setting statistically
significant constraints on the dust grains properties in this area. We find an
extinction curve considerably flatter than the standard Galactic one and than
those obtained before for the LMC. The derived value of Rv = 5.6 +/- 0.3
implies that in this region larger grains dominate. Upper MS stars span a
narrower range of E(B-V) values than RC objects, at variance with what has been
found elsewhere in the LMC.
