The Spotted Lake occurrence occurs in Spotted Lake near Richter Pass, located 9.8 kilometres from Osoyoos, British Columbia.

The showing is underlain by metasediments and metavolcanics of the Carboniferous to Permian Kobau Group. Schist, chlorite schist, quartzite, amphibolite and minor limestone comprise major lithologies of the Kobau Group. To the immediate south, granite and granodiorite of the Similkameen intrusions intrude the Kobau Group.

Spotted Lake covers approximately 8 hectares. When examined in 1938, the lake was covered with 15 to 20 centimetres of brine. The brine crystals form a bowl-like shape covering 50 to 60 per cent of the lake. The bowl-like shapes are 6 to 24 metres diameter, averaging 1.07 metres depth. The encircling mud rings are raised 10 to 46 centimetres above the crystal level, containing gypsum. The mud was determined to contain 70 to 80 per cent calcium sulphate. The following table summarizes analytical results of 5 surface samples from bowls. Sample 6 was analysed from mined surface crystals containing 40.26 per cent water but recalculated to a 100 water free basis (Bulletin 4 (1940), page 53).

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          1        2         3         4         5        6
MgSO4   50.02    44.67     47.25     47.04     47.21    57.58
Na2SO4  48.08    53.80     51.16     51.67     46.62    42.38
NaHCO3   0.49     0.57      0.56      0.48      0.50
Na2CO3                                 tr
NaCl     0.17     0.22      0.15      0.14      0.22
CaSO4    0.70     0.28      0.70      0.41      3.11
Insol    0.36     0.46      0.18      0.26      2.44
Alkalinity                                               nil
Cl                                                       trace
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The lake was estimated to contain 45,272 tonnes of hydrous salts of magnesium and sodium with 11,797 tonnes of sodium carbonate salts (Bulletin 4 (1940), page 55).

Records indicate 1361 tonnes of crystal (magnesium sulphite) were shipped by Stewart-Calvert Co. Ltd. from the Spotted Lake showing between 1915 and 1919 and shipped to Oroville, Washington for refining and sale (Bulletin 4 (1940), page 53).