Welcome to T-net.
I won’t be quite so disparaging about your item, but it’s certainly not made from opal and neither is it hundreds of years old.
There are 27 beads, so I would think it’s a ‘mala’… a string of prayer beads commonly used in Hindu, Jain, Sikh, Buddhist and Shinto religions. Their equivalent to a rosary.
A full mala necklace has 108 beads plus sometimes a 109th one of a distinctive size or colour but ‘pocket malas’ or ‘mala bracelets’ commonly have 27 or 54 beads and occasionally other multiples of 9 as a ‘sacred number’.
In more recent times the beads are often in the form of skulls and machine carved from things like ox-bone. If those are carved then they could be vintage to modern, but even vintage ones don’t have a value beyond about $50. If they’re moulded from resin or plastic then the value is zilch. Moulded ones can be readily identified from the fact that all of the beads in a string will be identical or at least a string of them will contain multiple beads which are identical to one another.