The South Talc prospect outcrops 3.5 kilometres southeast of the Talc Lake prospect (092ISW063), on a ridge that separates the Nahatlatch River from the Fraser River (Assessment Report 22665).
Significant talc occurrences were first reported in this area in the early 1950s by Geological Survey of Canada geologists. In 1973, talc was first reported in the Talc Lake prospect area by J.A. Chamberlain Consultants while conducting surveys for nickel, chromite and talc. Low grade nickel (0.2 per cent) was identified over a wide area and a zone of talc-magnesite mineralization was outlined. The zone is now referred to as the Talc Lake deposit. Between 1986 and 1988, 3000 hectares of ground was staked to cover potential talc (magnesite) lenses. In 1989 and 1990, Highland Talc Minerals Ltd. began systematically geological mapping the Talc Lake deposit. Late in 1990, a second talc zone referred to as the South Talc deposit was defined. Four exploratory drillholes were completed in 1990. Between 1991 and 1992, detailed geological surveys, surface stripping, and four follow-up drillholes were completed. In 1992, the North Talc deposit and 5 smaller satellite lenses were discovered. In 1993, a 100-kilogram bulk sample was taken from the South Talc deposit and a 120-tonne bulk sample was taken from the North Talc deposit shipped to Finland for Pilot Scale tests. In 1994, an additional 10 drillholes were completed on the South Talc deposit.
The area is underlain by phyllite, schist and foliated greenstone of the Permian(?) to Lower Cretaceous Bridge River Complex (Group) and by phyllite, schist and local conglomerate of the Upper Jurassic to Lower Cretaceous Relay Mountain Group. Pods of serpentinized ultramafics of the Bridge River Complex occur in fault and normal contact with both units. All units are intruded by stocks of Late Cretaceous quartz monzonite and granodiorite.
The Bridge River Complex and Relay Mountain Group are separated along the ridge by an intervening fault-bounded mass of serpentinite striking northwest for 5.9 kilometres, generally following the crest of the ridge, and varying up to 900 metres in width. The ultramafic rock is dark green to black and weathers buff to reddish brown. The serpentinite consists of fine grained, massive serpentine with minor carbonate and 5 per cent magnetite.
Since 1990, several systematic programmes were completed on the Talc Lake deposit that has included geological surveys, bulldozer stripping, trenching and drilling. A total of 8 drillholes totalling 746.3 metres have been drilled. The deposit consists of a steeply dipping, talc lens that has been traced along strike for at least 500 metres and varies in width from 50 to 120 metres. Drilling has tested the deposit to 128 metres depth and talc mineralization continues below. A relatively thin (0.5 to 3.0 metres) of overburden covers the deposit. Chlorite and minor pentlandite, pyrrhotite and magnetite are also present in the deposit.
The talc is pale green to white with a creamy buff weathered surface and contains small quantities of disseminated magnetite. Several sections of drill core were analysed by XRD and yielded an average grade of 68 per cent talc, 28 per cent magnesite with a low percentage of chlorite and ankerite (Assessment Report 22665). Thin sections show the rock to be composed of 50 per cent talc and 50 per cent carbonate and magnesite.
In 1994, a 100-kilogram composite sample was shipped to Finnminerals in Finland for pilot tests. Tests included were beneficiation from grinding, flotation, and micro-ionizing. Tests were also conducted on the chemical and physical properties of the talc, particle size distribution and paper-grade rheology tests. The final product produced included talc filler and extender with an average particle size 10 microns and brightness of 80 to 83 per cent (ISO), and a pitch control with an average particle size of 2 microns and a brightness of 83 to 85 per cent (ISO). A coating-grade, slurry talc pigment was also produced meeting rheological specification of light weight coated (LWC) papers (Assessment Report 23691). These tests were followed-up by LWC paper trial runs where several different weights of coated-grade papers were produced using the talc slurry. The results of some these tests are summarized as follows:
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Mineralogy Ore Concentrate
talc 56 94.9
chlorite 7 1.7
magnesite 35 3.1
dolomite 2 0.3
sulphides 0.03 0.02
magnetite 0.10 0.03
brightness 56 66
yellowness 15 11
Composition
Talc Magnesite
SiO2 62.2 MgCO3 78.2
Al2O3 0.04 CaCO3 0.1
MgO 29.4 MnCO3 0.1
FeO 2.6 FeCO3 21.3
NiO 0.22
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The low brightness and high yellowness are caused by the presence of iron hydroxide minerals, the latter being indicative of surface weathering.
Drill indicated reserves are calculated at 11,947,456 tonnes using a 50-metre area of influence (Assessment Report 22665). Geological inferred reserves are 1,387,650 tonnes for a total reserve estimation of 13,335,106 tonnes.
