The Hidden Treasure prospect is at an elevation of 1850 metres on Index Creek, a minor tributary of Gainer Creek, which flows southwest into Lardeau Creek. The Hidden Treaure (L.4718) claim is part of a northwesterly trending linear cluster of eleven tenures that cover the Mollie Mac [082KNW036], which is northwest of Gainer Creek, the White Quail [082KNW037], Hidden Treasure [082KNW106] and Index [082KNW038] occurrences. The Hidden Treasure claim is mid-way up the ridge on the west side of the creek.
The Hidden Treasure prospect was explored with the surrounding tenures in the early 1900s and there were several open cuts and adits on the property by 1914. The claim was acquired by Northern Inland Resources Limited in 1956 and it was explored along with the White Quail [082KNW037] and Index [082KNW038] prospects. However, the company concentrated most of its effort on the Index claim. The tenure has one long adit driven through barren rock.
The Trout Lake area is underlain by a thick succession of sedimentary and volcanic rocks of the Badshot Formation and Lardeau Group near the northern end of the Kootenay arc, an arcuate, north to northwest trending belt of Paleozoic and Mesozoic strata that is now classified as a distinct, pericratonic, terrane. The arc rocks are bordered by Precambrian quartzite in the east and they young to the west, where they are bounded by Jurassic-age intrusive complexes. They were deformed during the Antler orogeny in Devonian-Mississippian time and were refolded and faulted during the Columbian orogeny, in the Middle Jurassic. A large panel, the "Selkirk allochthon", was later offset to the northeast by dip-slip motion along the Columbia River Fault.
The Badshot formation is composed of a thick Cambrian limestone that is a distinctive marker horizon in the Trout Lake area. It is underlain by Hamill Group quartzite and it is overlain by a younger assemblage of limestone, calcareous, graphitic and siliceous argillite and siltstone, sandstone, quartzite and conglomerate, and also mafic volcanic flows, tuffs and breccias, all of which belong to the Lardeau Group. The rocks are isoclinally folded and intensely deformed, but only weakly metamorphosed. They occur as intercalated beds of marble, quartzite and grey, green and black phyllite and schist. Fyles and Eastwood (EMPE BULL 45) subdivided the group into six formations (Index, Triune, Ajax, Sharon Creek, Jowett and Broadview) of which the lowermost (Index) and uppermost (Broadview) are the most widespread. The Triune (siliceous argillite), Ajax (quartzite) and Sharon Creek (siliceous argillite) are restricted to the Trout Lake area. The Jowett is a mafic volcanic unit.
The Hidden Treasure occurrence is in a similar stratigraphic and structural setting to the White Quail [082KNW037], lower down the hill, and the Index [082KNW038] occurrence higher up the hill. The tenure is underlain by green phyllite, metatuff and limestone at the top of the Index Formation and by black siliceous argillites, cherts and phyllites of the overlying Triune Formation. Up slope to the southwest, the section passes through Ajax quartzite into siliceous argillite and phyllite of the Sharon Creek Formation. The Triune and Ajax formations thin dramatically to the southeast and the Ajax Formation pinches out on the Index claim (L.3956). The rocks are isoclinally folded and highly deformed. They have an axial plane cleavage that strikes to the northwest and dips at a steep angle to the southwest.
The Hidden Treasure area is underlain by steeply-tilted, greenish schists that are interbedded with bands of limestone near the top of the Index Formation. On the Index tenure, the "Molly Mac" limestone is present in two parallel bands that are probably fold repetitions of each other. They dip steeply to the southwest. The southwest band is barren and forms the core of a small anticline. The limestone passes under phyllite to the southeast. The northeast band is mineralized. It is from 15.24 to 27.43 metres wide and pinches out to the south of the claim. The geology is probably similar lower down the hill.
On the Hidden Treasure claim, the mineralization is on fracture planes in limestone parallel to its strike and dip, and also on a series of joint planes which strike 065 degrees and dip at 23 degrees to the northeast. Sulphide replacements occur at the intersection of fractures and commonly comprise bunches of galena. Where a small canyon cuts through the limestone, it was found to be heavily impregnated with pyrite and disseminated galena over its entire width. A sample across 1.52 metres of mineralized limestone in an adit at 1800 metres elevation assayed a trace of gold, 48 grams per tonne silver and 8.7 per cent lead. Uphill to the southeast, there is a 2.4 metres deep shaft at 1900 metres elevation that also exposes limestone heavily impregnated with iron oxide, but also contains pyrite and galena. A "small" sample taken across 1.52 metres in 1914 assayed a trace of gold, a trace of silver and 4 per cent lead. On the footwall side of the limestone, there is a fault occupied by a light coloured dyke that contains quartz and calcite and is also mineralized with galena and pyrite. The dyke is 0.46 metres wide and a sample taken across it assayed trace gold, 6.86 grams per tonne silver and 1.5 per cent lead. Elsewhere on the property, there is an adit cut through the footwall phyllites.
When Northern Inland Resources Limited acquired the property, it focused most of its attention on the neighbouring Index claim, where it found siderite alteration zones mineralized with disseminated galena on the hanging wall, in the centre and on the footwall of the northeastern band of "Molly Mac" limestone. The zones are between 0.91 and 3.0 metres wide and they extend for several hundred metres along strike [082KNW038].
During 2006 through 2009, Mineral Mountain Resources Ltd. completed programs of prospecting, geochemical (soil, silt, talus fines and rock) sampling and an airborne geophysical survey on the area as the Kootenay Arc property.
