I made this map around 1980 and added the locations in blue in December 2021.
The Midwest Lake orebody is indicated in black as "OREBODY",
the Midwest A deposit by the blue letter A, the Roughrider deposit including the J-zone deposit by the blue letter R,
and the Huskie zone by the blue letter H.
Note that the official name of this lake is South McMahon lake. Geologists call it Midwest Lake after the name of the diamond drilling company
that did the intial drilling.
Note the high radon values near the Midwest orebody and low values elsewhere.
The radon anomaly was confirmed in 3 different summers by 3 different operators,
all before the orebody was discovered by drilling.
First (1969), Bondar-Clegg carried out a water survey at a
spacing of one sample per square mile. This survey included only one sample
near the orebody and it ran 19 pCi/L in radon, which they identified as "probably
anomalous". This sample was not anomalous in uranium.
Later (1972), in a more detailed survey, I collected water samples by canoe from shallow water around the edge and analysed them
for radon in a tent.
My results are shown in the figure.
Several years later the orebody was discovered by the drill (shown in solid black on the figure)
If the water in Midwest Lake had been a few feet higher,
the radioactive boulder train would have been submerged, but the orebody
could have been found with a radon survey. We have similar results from