The Tulameen River flows northward for 30 kilometres from the Cascade Mountains to Grasshopper Mountain, where it changes course and continues eastward for 10 kilometres to the town of Tulameen. The river then flows southeast for 25 kilometres before entering the Similkameen River at Princeton.

The upper part of the river runs through a wide valley extending from its headwaters in Paradise Valley southward to Champion Creek. The river continues through a narrow rock-walled canyon between Grasshopper and Olivine mountains to the mouth of Olivine (Slate) Creek. Here, a broad valley floor with deep gravel deposits opens up and continues past the towns of Tulameen and Coalmont to a point 2 kilometres below Granite Creek. The river then cuts through a canyon, where extensive gravel deposits are relatively scarce. About 5 kilometres west of Princeton, the river enters a broad valley and flows over a gravel bed with gravel benches on either side, extending to the Similkameen River.

Gold and platinum deposits have been found over the lower 40 kilometres of the river. Most recorded production and exploration has occurred along two stretches. The upper stretch begins about 2 kilometres west of Tulameen and continues up the river for 12 kilometres to the mouth of Champion Creek. The lower stretch begins at Coalmont, just above the mouth of Granite Creek, and continues southeast for 19 kilometres to Princeton. See Tulameen River Placer (092HNE199) for a detailed review of the upper section.

Metals found along the Tulameen River tend to occur in old sinuous channels buried deep below glacial gravels, which contain only spotty values. Gold occurs in rough, angular or slightly flattened and rarely well-flattened nuggets. Some of the nuggets contain abundant white quartz. Platinum forms small rounded grains of uniform size. They are smaller than the gold nuggets and are commonly pitted. Larger platinum nuggets often have a coating or included crystals of cumulate chromite, sometimes with intergrown magnetite and inclusions of olivine (CIM Bulletin, June, 1976). The gravels worked along the river also yielded black sands containing fine platinum, in addition to gold. The ratio of gold to platinum recovered in this part of the river is about 4:1, but decreases upstream (Geological Survey of Canada Memoir 243, page 59).

Black sands produced by a dragline 4 kilometres above Princeton assayed 251 grams gold per tonne and 40.1 grams platinum per tonne (Minister of Mines Annual Report 1925, page 216). Farther upstream, about 3 kilometres below Coalmont, a sample of panned black sand assayed 27 grams gold per tonne and 21 grams platinum per tonne (Minister of Mines Annual Report 1929, page 281). A series of shafts and pits at this location below Coalmont encountered gravels averaging 1.1 grams of gold equivalent per cubic metre for combined gold and platinum (Minister of Mines Annual Report 1929, page 281). Similar workings at Petersen Flat, 5 kilometres west of Princeton averaged 1.2 grams of gold equivalent per cubic metre for combined gold and platinum (Minister of Mines Annual Report 1924, page 176). Measured geological reserves on the Ruby lease, 6 kilometres below Coalmont, are 268,000 cubic metres grading 1.38 grams of gold equivalent per cubic metre for combined gold and platinum (Property File - N.C. Stines, 1929, page 6). Bulk sampling in the immediate vicinity produced 77.8 grams of coarse gold from 15.3 cubic metres of gravel (Property File - R.B. Stokes, 1980, page 1). Two samples of platinum from the Ruby lease analyzed as follows (in per cent) (Minister of Mines Annual Report 1930, page 212; N.C. Stines, 1929, pages 43, 44):

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Gold 0.58 3.54

Platinum 68.74 60.37

Palladium 0.31 -

Iridium 2.22 15.99

Osmium - 6.81

Rhodium 0.48 6.06

Ruthenium - 7.23

Insoluble metals 8.1 -

(osmiridium, etc.)

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Production of placer gold was first reported in 1877, and may have commenced as early as 1860. By 1887, most of the shallower gravel deposits mined along the Tulameen River were reported to be exhausted (Minister of Mines Annual Report 1887, page 278). High platinum prices during the mid to late-1920's prompted a revival of placer mining along both the upper and lower sections of the river. Three prominent operations, located 3 (Guest lease) and 6 (Ruby lease) kilometres below Coalmont and 4 kilometres above Princeton (National Holdings Ltd.), were active between 1924 and 1929 on the lower part of the river. Production from the Ruby lease for 1926 amounted to 778 grams of gold and 280 grams of platinum (Minister of Mines Annual Report 1926, page 230). Minor production occurred during the 1940's and 1950's, largely within 5 kilometres of Princeton. This activity was centred 3 kilometres west of Princeton, where for example, R. Haigh recovered 1534 grams of gold and 420 grams of platinum from 760 cubic metres of gravel in 1941 (Minister of Mines Annual Report 1941, page 92). The adjacent Ashley deposit produced 900 dollars in gold and platinum weekly in 1941 from a paystreak up to 0.9 metre thick, comprised of well-bedded, partly cemented gravels, overlain by 3 metres of glacial material (Geological Survey of Canada Memoir 243, page 59). Gold production for the entire river between 1885 and 1945 is estimated at 297,000 grams. See Tulameen River Placer (092HNE199) for yearly production figures.