The True Blue (L.4859) occurrence is located on a northeast facing slope of True Blue Mountain, approximately 5 kilometres southwest of Kaslo.

The area is underlain by basaltic volcanic rocks of the Carboniferous to Permian Kaslo Group and limestone, slate, siltstone and argillite of the Upper Mississippian to Permian Milford Formation.

Locally, two massive sulphide horizons or lenses, averaging 25 to 35 centimetres thick but combining locally to 1.2 metres thick, occur along the contact between volcanic and sedimentary rocks. Mineralization consists of pyrite, pyrrhotite and chalcopyrite with minor galena and sphalerite hosted in sericite schist. The sulphide horizon(s) is overlain by 1.0 to 2.0 metres of strongly sericitized and weakly pyritic volcanic tuff. Well-defined thrust and extensional faults are reported in underground workings.

In 1979, a chip sample from a mineralized lens assayed 0.9 gram per tonne gold, 37.7 grams per tonne silver, 0.12 per cent lead, 2.76 per cent zinc and 6.75 per cent copper (Property File - D.H. Watkins [1985-01-01]: Correspondence re: True Blue Property).

Between 1898 and 1902, 96 tonnes produced 8544 kilograms of copper, 5629 grams of silver and 124 grams of gold.

The occurrence was discovered and explored with 125 metres of underground workings near the turn of the 20th century. In 1979, Esso Minerals completed a program of geological mapping and ground geophysical surveys on the area. The property was optioned by Saskatchewan Mining Development in 1982, and a program of airborne geophysical surveys, geological mapping and soil sampling were completed. In 1986, MineQuest Exploration Associates examined the property. Sultan Minerals Inc. optioned the property in 1998 and drilled one hole in 1999. Results were reportedly disappointing, and the option was dropped.