Just thought I’d share this example of how the virgin wash layer looks around Lisle which the old timers were chasing. The layers are quite clearly defined, on the bottom you have the light coloured decomposed granite which is very soft and easy to dig almost like chalky sand. Right on top of that you can see the thin stained red gravel layer and this is where the richest gold lies. It’s very hard packed almost cemented together.
Sometimes you can expose these layers in the bottom of old leads and faces or excavator test holes but in my experience they always contain pretty poor gold which is probably why it’s still there. One day i’ll find a good one…
I like the way you are investigating the wash. I don’t know where the original reefs were located that shed the Lisle gold. Maybe they are now weathered away?
From watching Yukon Gold I would say look for the old streams and river banks, now above and away from the present day streams. A reddish ‘iron layer’ is a good sign apparently.
Very few gold bearing reefs found in Lisle either by the old timers or modern prospecting. It’s almost exclusively an alluvial gold field and I believe the dominant theory on the origin of the gold is by way of ‘secondary enrichment’.
The leads I have found are quite variable, some with large cobbles and full of quartz and some almost devoid of quartz, but they all have that red band sitting directly on the old granite.
