This is a traditional Indian mangalsutra, a sacred necklace worn by married Hindu women. It typically features black beads strung together with gold and is believed to protect the marriage from evil influences and bring prosperity.
This particular design has:
Black beads arranged in pairs along the chain.
Gold spacers with intricate detailing.
A modern pendant combining gold with diamond or cubic zirconia baguette-style stones, arranged in an elegant, contemporary pattern.