Crystal Peak (Mount Riordan) garnet deposit, Apex Mountain, Osoyoos Mining Division, British Columbia, Canadai

Regional Level Types
Crystal Peak (Mount Riordan) garnet deposit	Deposit
Apex Mountain	- not defined -
Osoyoos Mining Division	Division
British Columbia	Province
Canada	Country

The Crystal Peak garnet deposit is located on Mount Riordan, about 2 kilometres west of the Apex Mountain ski terminal, or 26 kilometres west-southwest of Penticton, British Columbia, in the Osoyoos Mining Division.
There is a description of the property, including regional geology, on the British Columbia “Minfile” site, current to 2008. Portions relative to geology are quoted below:
“The deposit is hosted in a roof pendant of carbonate-rich sediments (limestone) of the Upper Triassic French Mine Formation, Nicola Group that has been almost completely replaced by garnet-rich skarn. The roof pendant is intruded from the north and east by hornblende porphyritic granodiorite of the Middle Jurassic Bromley batholith (locally known as Mount Riordan stock), part of the Middle Jurassic Nelson intrusions (Bulletin 101 [Ray and Webster, 1997]).
An elongate mass of garnetite trending north-northwest for up to 900 metres lies centred on Mount Riordan. The deposit contains three major, high grade zones (60 to 100 per cent garnet) outcropping over a total area of 3.35 hectares. Remnant bodies of microdiorite up to 30 metres in diameter are scattered about a broad zone lying in the centre of the skarn.
The skarn consists of massive and coarsely crystalline garnetite comprised of approximately 90 per cent andradite and 10 per cent grossularite [sic]. Garnet crystals typically contain andradite-rich cores and grossularite-rich margins. The garnet is usually brown and green, with minor black, red-brown, pink and yellow-green varieties. Diopside, quartz, calcite, epidote, actinolite, hedenbergite, clinopyroxene and magnetite occur in relatively low quantities. Traces of chlorite, wollastonite, scheelite and various sulphides are also present. Total impurities amount to 5 to 15 per cent of the skarn. Calcite occurs as rare flat lying or gently dipping marble layers, as interstitial blebs 1 to 3 millimetres in diameter, and as small veins developed near the summit of Mount Riordan.
Scheelite mineralization tends to occur as small crystals less than 1 millimetre in diameter sparsely disseminated or clustered throughout the skarn, and as blebs, coarse crystalline masses and veinlets up to 5 centimetres in width and 3 metres in length near the summit of Mount Riordan. A grab sample of scheelite-rich mineralization taken near the summit contained in excess of 5 per cent tungsten (Fieldwork, 1987 [Ray, et al. 1988, p. 76, Table I-5-5]). Some scheelite-rich sections also contain coarse axinite.
Pockets, irregular veinlets and blebs of magnetite intergrown with variable amounts of pyrrhotite, pyrite, chalcopyrite and traces of bornite are also present in the skarn. This mineralization is best developed in a series of gossanous zones found along a west trending linear structure in the northern half of the deposit. A grab sample of magnetite-rich mineralization assayed 1.69 grams per tonne gold, 19 grams per tonne silver, 0.74 per cent copper and 0.11 per cent zinc (Fieldwork, 1987 [Ray, et al. 1988, p. 76, Table I-5-5]).”
Giles Peatfield comments:
This area, initially explored as a copper-gold occurrence, was described by Robertson (1902) who reported ‘copper pyrites’ (chalcopyrite), ‘garnetite’ and pyrrhotite. McCammon (1954) reported the discovery of scheelite mineralization on the ‘Billie Goat, Shamrock, etc.’ claims on Mount Riordan. This tungsten discovery was apparently toward the last years of World War II, but there was little follow-up work. Note that McCammon’s spelling ‘Billie Goat’ is incorrect; the claim was Crown Granted (‘patented’ for USA readers) as the Billy Goat in 1905 – see Annual Report of the British Columbia Minister of Mines for the year 1905.
This garnet deposit never reached the production stage. Extensive drilling outlined a substantial resource of attractive grade garnet-bearing skarn, with material suitable for industrial usage, primarily sand-blasting. Notwithstanding this, the project encountered passionate protests from local residents and from the nearby Apex-Alpine ski development. The British Columbia Government sided with the protesters and the project was denied approval. The resource, as stated by Minfile, was as follows:
“Indicated reserves at the North zone are 17,955,000 tonnes grading 80 per cent garnet; indicated reserves at the West Zone are 11,848,200 tonnes grading 78 per cent garnet; indicated reserves at the South zone are 10,663,380 tonnes grading 77 per cent garnet (Mineral Development Assessment Process - Crystal Peak Garnet, Stage 1 Report, March 1991).”
Note that these resources, although carefully prepared, would not necessarily be compliant with National Instrument 43-101 guidelines, which have changed since the resource estimates were made.

Comments on the Minerals Reported:
Note that all but three of the minerals listed were reported by Ray, et al. (1992). The exceptions will by noted in the comments below. I have given comments for those minerals with special characteristics. Others in the list are those one would commonly expect in a deposit of this type.
Bornite: Ray, et al. (1988; 1992) reported that bornite is present in only trace amounts.
Chalcopyrite: Robertson (1902) reported ‘copper pyrites’; Ray, et al. (1992) described chalcopyrite as a minor constituent in the garnet skarn.
Clinopyroxene Subgroup: McCammon (1954) reported diopside in skarn; Ray, et al. (1992) reported that “Microprobe analyses indicate that the pyroxenes at Mount Riordan . . . contain less than 1.3 wt percent MnO . . . . The pyroxene crystals show no optical or chemical zoning and range from Hd41 to Hd51 mole percent . . . .”
Feldspar Group, var. orthoclase: Ray, et al. reported that in the unaltered portions of the Mount Riordan stock orthoclase is altered and has marked optical zoning.
Feldspar Group, var. plagioclase: Ray, et al. reported that hornblende crystals in the Mount Riordan stock contain inclusions of plagioclase, quartz and pyrite; and that coarse plagioclase ranged in composition from An15 to An42.
Garnet Group: Keep (1990) reported that “Garnets from 32 samples from the Mt. Riordan property were analyzed with an electron microprobe (EMP) at the University of British Columbia.” Given the subject matter, it is worth quoting her conclusions in full. “All of the garnets from the Mt. Riordan Peak property are part of the andradite-grossular transition. Of the 32 samples analyzed, 27 comprise grains with an andradite component greater than 65%. Only 5 samples have garnets with a high grossular component. The samples can be subdivided into 3 main groups including those that have a high andradite component and minimal compositional variation, those with high andradite concentrations and an expanded range of composition, and those that are mostly grossular-rich with a large compositional range. Compositional variation due to zoning involves both a slight increase and a slight decrease in andradite towards the rim. However, these increases and decreases in composition are small, in most cases representing less than a 10% change in the andradite component.” In overall terms, it is safe to refer to this as an andraditic skarn deposit.
Hematite?: Grond and Wolfe (1990) reported ‘hematite staining’ in drill core, but gave no details.
Jarosite: Ray, et al. (1992) described jarosite as a weathering product of the sulfide minerals, but gave no specific data.
Malachite?: Grond and Wolfe (1990) reported ‘copper staining’ in drill core. I have interpreted this as probably malachite.
Mica Group, var. biotite: Ray, et al. reported biotite as a constituent of the Mount Riordan stock.
Mica Group, var. sericite: Grond, et al. (1991) reported sericite as an alteration product in diopside in the garnet skarn.
Powellite: Ray, et al. (1988) reported powellite as ‘tentative’; in 1992, they reported that it had been X-ray confirmed.
Wad?: Grond and Wolfe (1990) reported ‘manganese staining’, in some cases with dendritic growth patterns. I have chosen the generic term ‘wad’ for this occurrence.

References

Other Databases

Link to British Columbia Minfile:	082ESW102