The pearls look like Akoya and the clasp has the Mikimoto logo...the style of necklace is not very common, yet not rare....can't recall how its called.
It looks beautiful, very well matched and arranged.
Well, at first sight they seem to be Potatoe freshwater pearls from China...but they could also be natural baroque pearls.
Did she leave any information about the pearls? Source/origin?
Since the pearls belonged to an Australian couple and are from some time ago, and antique dealers...there is a chance those are actually natural pearls.