Black Onyx semi-precious stone tumblechip beads. These irregular shaped gemstone beads are black in colour and believed to promote steadfastness and determination. Black Onyx is a banded stone that is commonly coated with a shiny black layer for jewellery use, as is the case with these beads. These gemstone beads are strung on a 36 inch/90cm strand of monofilament. This a very economical way of purchasing semi precious beads.