Hi Ziede,
I am a master of aquaculture and for taxonomy issues I have to rely on people who work in our Australian Museum for these issues. They have nominated these "oysters" (I will call them oysters when in fact they are a mussel as it is the terminology that is commonly used down under) as "Pinctada imbricata".
They may not be what the pearls look like in the northern hemisphere but they are what we had at the time the photograph was taken. A possible reason why there is this difference is because this project was the first in the southern hemisphere and therefore the possibility of the pinctada imbricata could have spread from here or there.
As I have said previously in the forum we did have some blues and pinks about a similar colouring as yours or maybe a bit lighter. I have also seen some good olde Australian colours here (a green and a gold)which are my favourite colours but then again I am biased. these are all natural colours. Unfortunately, I do not have any photographs of these.
The pearl that is cut in half I am trying to get a measurement on it for you with an approximation of the depth of the nacre. I will post that information when I have it.