Hi Bernard, I am not an expert on aventurine, but here are my observations from the pictures (which is always tough) and my understanding of aventurine, both definition and todays accepted terms and application.
It appears to me in the images that the "pieces" appear more to be "gathers" of fine particulates than flakes", but You can better judge than I since you can hold and look at it.
If they are in fact "flakes" then based on the initial development of aventurine, flakes would not qualify as aventurine.
The initial use of aventurine was an attempt with glass to simulate the look of Aventurine Quartz, which is most commonly found in green, but is also found in other colors.
The shimmering look of aventurine quartz is caused by platy mineral inclusions within the stone which gives it a shimmer referred to as aventurescence. The inclusions are a form of Mica
Initially, very fine particulates of copper were added to glass and evenly dispersed within the glass to simulate aventurescence, which occurs consistently throughout aventurine quartz, and not in pockets.
The term now seems to be generically applied to the use of gold and silver, and also to larger flakes of foil which are "technically" not aventurine.
Although the term is applied to work such as this piece, technically it should look like the attached image..... although the image is a later version of aventurine, obviously Italian, and done with gold instead of copper...
If your piece does have flakes, I personally would refer to it as foil inclusions, and not aventurine.
I hope this helps....
Craig