The ornamental design for a diamondnecklace, substantially as shown and described.
FIG. 1 is a top plan view of a diamond necklace showing my new design
portions of the continuous neckchain being broken away for convenience of
illustration;
FIG. 2 is a side elevational view thereof; and
FIG. 3 is a sectional view as seen from the plane 3--3 in FIG. 2.