Another self reminder of things to look for, this time for sapphire fossicking.
A lot of what you pull up will be quartz and possibly topaz, sapphire is much rarer but sticks out when its there. The method for finding them can be looked up on youtube (this video gives a rough idea of how its done.
If you're doing your screening properly you'll end up with all the black stuff on the top when you flip your screen over, and hopefully have some sapphires or topaz.
Sapphires are heavier than the other rocks and sand that will flow down the river, so you look for similar areas as you would for alluvial gold.
You need to dig down a fair way into the water, its not uncommon to be in the water waist deep. In Tassie's rivers you might want a wetsuit.