Cassiar Beryl, Horseranch Range, Liard Mining Division, British Columbia, Canadai

Regional Level Types
Cassiar Beryl	Occurrence
Horseranch Range	Mountain Range
Liard Mining Division	Division
British Columbia	Province
Canada	Country

The Cassiar Beryl (MRX) occurrence is located 10 kilometres east of Dease River in the Horseranch Range, 85 kilometres south of Watson Lake, Yukon and 125 kilometres north-east of Dease Lake, British Columbia.
The following quote is from B.C. Government site “Minfile”- Minfile No. 104P 024, current to 2014:
“The Cassiar Beryl occurrence is underlain by rocks of the Upper Proterozoic Ingenika Group, Lower Cambrian Atan Group and Ordovician to Lower Devonian Sandpile Group. The Ingenika Group consists mostly of medium to high grade metamorphic grade (garnet to sillimanite-orthoclase grade) schists, quartzites, marble and minor orthogneiss. The overlying Atan Group consists mainly of quartzite. The Cambrian to Ordovician Kechika Group is composed mainly of chloritic phyllite and schists and the Sandpile Group of dolostones and dolomitic limestones. The igneous rocks in the Horseranch Range consist of mid-Cretaceous and Eocene age granitic dikes, pegmatite, ultramafic and mafic rocks. Granitic dikes occur in the Ingenika Group. Ultramafic and mafic rocks are exposed as undeformed bodies in the Ingenika and Kechika groups and as mylonitized to undeformed bodies in the mylonite zones. A mylonite zone, trending roughly 325 degrees, is interpreted to be a Riedel shear or splay of the Cretaceous dextral slip Kechika fault.
Pegmatite dikes, commonly parallel to foliation, intrude quartzites and mica schists in a zone 750 metres wide and 5 kilometres long. The pegmatites are composed of feldspar, quartz, muscovite, lesser amounts of tourmaline and garnet and minor pale green beryl. Pegmatites are rarely zoned, with muscovite-tourmaline-rich margins and quartz-rich cores. Beryl occurs as hexagonal prisms 0.5 to 1.0 centimetres across and 1 to 2 centimetres long. Overall average beryllium content of the pegmatite was visually estimated to be less than 0.1 per cent (Minister of Mines Annual Report 1955, pages 9, 10).
In the showing area, the field relationships between felsic dikes and ultramafic rocks relative to mylonitization are important criteria for beryl exploration. The ultramafics form sharp contacts with the surrounding rocks, and it is not clear whether the porphyritic, biotite-bearing ultramafic complex is a sliver of a single body or part of a larger underlying mass.
Most of the beryls at the showing are found in coarse grained blocks of granite dike and pegmatite in talus slopes of the Camp Creek valley that were probably derived from local dikes. Beryl is observed in zoned pegmatites as well as in fine to medium grained homogenous granitic dikes. Beryls have not been observed in foliated dikes. Beryl crystals are pale blue to pale watery green in colour, translucent and vitreous lustre. Rare crystals of beryl are colourless and transparent. Individual beryl crystals vary in size from 0.1-5.0 centimetres in length (along the C axis of the hexagonal crystal) and from 0.1-3.0 centimetres in width (along the a1, a2 and a3 axis of the hexagonal crystal). In some locations, about 5 per cent of the granite/pegmatite is composed of beryl crystals (Assessment Report 28030).
The Cassiar Beryl property was previously worked on by Esmeralda Exploration International Inc. in the 1990s. Work carried out by B. Wilson led to the cutting of several pale blue beryl gems, the largest stone having a weight of 0.94 carat. In 2005, A. Kikauka conducted geological mapping and rock specimen sampling.”
Note that some kilometres to the north there is a broadly similar occurrence (Harvey Lake – Minfile No. 104P 122).
Comment by Giles Peatfield regarding the locality name:
Pike (1896), writing of his travels in the Cassiar country, noted that “The usual winter road follows the Dease for 30 miles, and then strikes off to the eastward, passing through an open grassy country, with numerous lakes, and skirting the foot of a high range known as the Horse Ranche Mountains. It is here that the horses used for packing provisions to the outlying mining camps in the summer pass the long winter, scraping away the snow in search of the bunch-grass, usually coming out in good condition in the spring, although once or twice things have gone wrong, and many of the band were missing when the snow went off.”
Comments by Giles Peatfield regarding some of the minerals listed:
Garnet: This has been described by Wilson (1998) as “grossular – gem hessonite”, and by Kikauka (2005) as “almandine-pyrope? 'rhodolite'”; no further details are available.
Hornblende: Reported only by Wilson (1998), as a constituent of mafic gneisses.
K-feldspar: This has been reported by several workers as either orthoclase or microcline (or both).
Olivine: Reported only by Simandl, et al. as occurring in pyroxenite.
Phlogopite: Wilson (1998) reported either biotite or phlogopite in altered ultramafic rocks.
Pyroxene: Reported by Wilson (1998), but with no further data.
Tourmaline: Most workers simply mentioned it as “black”; Kikauka (2005) described it as “shorl”.
All other minerals not mentioned in these comments were identified by Payne (2005) in thin and polished thin sections.
Comments by Giles Peatfield regarding some of the rock types listed:
The rock types listed are field names, mostly derived from Simandl, et al.

Other Databases

Link to British Columbia Minfile:	104P 024

Other Regions, Features and Areas containing this locality

References