Still haven't managed to catch my mum.

But when she does the olives they are generally as hard as a rock.And they stay hard for weeks. So perhaps your are too ripe...

But on saying that she collects them all - even the ones ripe enough to fall to the ground - so perhaps they simply need pickling for different lengths of time. Interestingly, that dark colouring of the water is exactly what my mums look like after a few weeks in the jar.

Anyway, you'll know once you open the jar and taste them whether it has worked or not.