First of all, let's get one thing perfectly clear..........
Even tho identifying Aventurine may sometimes be an aDventure,
there is NO "d" in Aventurine.

Aventurine is a form of quartz and is occasionally called a quartzite.
The most common color is different shades of green caused
by the inclusion of fuchsite, a chrome bearing variety of muscovite.
There must be some trace of mica in the rock for it to be
called aventurine. And there are usually some trace signs of
pyrite as well.
Other colors of aventurine include orange, brown, yellow,
blue and gray. The orange and brown colors being caused
by hematite or goethite staining.
The different "mixes" of this rock make it one many have a
hard time identifying. You can just look at the many shades
of green to get an idea why it can be so confusing.

Here are some pieces found at the gem sluice recently.
In the first pic the natural rough rock end pieces are to
either side of the polished pieces. I don't know if the
close-up pics will help you much but I was trying to show
some of the mica and pyrite inclusions.
Both rocks are aventurine even tho the lighter one could
probably pass as a jade to most people.