The
most interesting result of the serpentinisation of the olivine is the
production of secondary rutile. Rutile never appears in the fresh
olivine, but as serpentinisation begins rutile needles form along the
border of the decomposing olivine, their longer axes being parallel to
the outlines of the original crystal. When serpentinisation has
proceeded so far that only an inner kernel of olivine remains, rutile
needles may be formed all around this inner kernel, lying in the
serpentine pseudomorph, not irregularly as if ordinary enclosures, but
in fixed crys-tallographical directions parallel to the olivine
outlines. Figures 11 to 15 exhibit this secondary rutile.
