Family Farm Mica Deposit, Mica Peak, Fort Grahame, Omineca Mining Division, British Columbia, Canadai

Regional Level Types
Family Farm Mica Deposit	Deposit
Mica Peak	- not defined -
Fort Grahame	- not defined -
Omineca Mining Division	Mining Division
British Columbia	Province
Canada	Country

Latitude 056º 33' 19'' North; Longitude: 124º 44' 03'' West. The mica-bearing pegmatites occur near the top of Mica Peak, about 8 kilometres south-west of the location of Fort Grahame (now submerged below the waters of Williston Lake) and 170 kilometres north-west of Mackenzie, British Columbia.
Giles Peatfield comments:
There is a brief description of the occurrence, listed as a past producer, and of the regional setting, on the British Columbia “Minfile” site, current to 2021. Parts of this description are quoted below:
“The area is underlain by regionally metamorphosed miogeoclinal rocks of the Neoproterozoic Ingenika Group. In the vicinity of the showing, these metasediments largely comprise quartzites and schists.
According to Geological Survey of Canada Summary Report 1927 [Dolmage 1928], all mica-bearing pegmatites in this area consist of feldspar and quartz, and small amounts tourmaline, garnet, and pyrite. The tourmaline occurs as small, well formed, jet-black crystals frequently arranged in rosettes, and commonly found in the country rocks adjoining the pegmatites. The garnets are bright ruby-red in colour. One pegmatite dike in the area is also reported to have contained a well-developed crystal of pale bluish green beryl.
The Family Farm occurrence comprises two concordant dikes of white pegmatite, intruding schist and consisting of mostly muscovite, quartz, and feldspar. The larger dike forms an elongate ellipsoid that strikes 150 degrees, dips 70 degrees west and plunges up to 12 degrees towards 150 degrees, with long and intermediate axis of 100 metres and 12 metres, respectively. This dike varies up to 10 metres wide. Muscovite crystals, up to 13 centimetres in diameter, occur in the pegmatite, with the larger grains generally within 1 metre of the wallrocks. The muscovite is reported to be of excellent quality despite some surface weathering.”
There was a very minor amount of production from the deposits in the early years. Minfile reports that 2.3 tonnes of mica were mined; Lay (1927) wrote, quoting Manager Gordon F. Dickson, “I then formed two new camps, one on Low (east) Mica mountain and one on High (west) Mica mountain, and from workings at these places about 21/2 tons of mica was extracted, which was cut before being brought out and reduced to about 700 lb. and shipped to Edmonton.”
Gabrielse (1975) presented a summary of potassium-argon age determinations for various rocks in the Fort Grahame east-half map-area. Of these, only two were from the general area of the mica deposits in question. Both are from a few kilometres south of the principal mica occurrences, just south of Mount Henri. The first age, from muscovite in a pegmatite, was 49±4 Ma; the second age, a pair, from biotite and muscovite in gneiss, was 47±3 for both minerals. Gabrielse (1975) assigned these rocks to the upper Proterozoic; Ferri et al. (1992) called them late Proterozoic. It would seem that there must have been a thermal event in Tertiary time to re-set the mica ages.
A word regarding the location of the deposit seems justified. Allan (1920), writing about the mineral resources of Alberta, acknowledged that this mica occurrence is actually located in British Columbia. The rationale for including it in his report was that “No economic deposit of mica occurs in Alberta, but the recent discovery of muscovite of good quality towards the head of Peace river in British Columbia, which is tributary to Alberta, is sufficient reason for including a description of the occurrence of this mineral in this report.” The deposit was being tested by Edmonton interests, and it seemed that the most reasonable route for shipment of product would be down the Peace River to the terminal of the Edmonton, Dunvegan and British Columbia railway at the town of Peace River and thence south to Edmonton. See also the comment below regarding the mica group.
Giles Peatfield Comments on the Minerals Reported:
This list, while probably incomplete, includes those minerals specifically reported as occurring in the pegmatites and surrounding rocks in the mica deposit area.
Amphibole group: The only reference to an amphibole was by Spence (1929), who wrote that “The pegmatite dykes sometimes contain garnets and large crystals of hornblende, . . . .” Other writers did not mention amphiboles.
Beryl: Dolmage (1928), describing the pegmatites, wrote that “. . . in one dyke a well-developed crystal of pale bluish green beryl was found.”
Feldspar group: Describing the pegmatites, Dolmage (1928) wrote that “The feldspar is largely orthoclase with a very small amount of albite. The orthoclase crystals range in size up to 8 or 10 inches and invariably are pure white. Some are slightly translucent; others have a pearly opalescence due to a very fine microperthitic structure. Many of the orthoclase crystals contain a large amount of graphically intergrown quartz.”
Garnet group: Dolmage (1928) described garnets in the pegmatites as “ruby red”; other writers simply reported “garnets”. No specific data are available.
Limonite: Allan (1920), describing the muscovite crystals, noted that they in many cases had a surface coating of “iron oxide”, which I take to mean limonite.
Mica group: This is the mineral group of most economic importance for this deposit. Both biotite and muscovite have been reported; the latter is the important one. Allan (1920) described the muscovite in some detail, as follows: “The mica is associated with quartz and feldspar and occurs in pegmatite dikes which appear to have a northeast and southwest trend. The country rock is micaceous schists. Blocks or ‘books’ of mica are strewn about the surface due to the disintegration of the pegmatites. Blocks of mica roughly defined by crystal faces were obtained from a fraction of an inch up to a maximum of eleven inches in diameter. Both the optical properties and the chemical analysis show that the variety is muscovite of high quality. The mica has an eminent cleavage, high degree of transparency and is highly flexible. Microscopically, the muscovite is free from all flaws, stains and internal structures that affect the market value of the mineral, such as ‘ruled,’ ‘herring-bone,’ or ‘A’ structures. The yellowish stain on the blocks is entirely superficial and due to a coating of iron oxide about the margins of the blocks resulting from exposure on the surface of the ground. This color is not present in the centre of the blocks or in the unweathered blocks in the pegmatite. There would be considerable waste in trimming the blocks which are now weathered on the surface.”

Pyrite: This is an uncommon mineral at this location. It was reported by Dolmage (1928) and by Mulligan (1960).
Quartz: This is a major constituent of the pegmatites. Both Dolmage (1928) and Mulligan (1960) describe it as “smoky”. It may well be that Mulligan was, as in the case for pyrite, simply relying on the report of Dolmage.
Tourmaline group: Dolmage (1928) described the tourmaline as follows: “The tourmaline occurs as small, well-formed, jet black crystals in many places arranged in rosettes, and is commonly found in the country rocks adjoining the pegmatites.”
Giles Peatfield Comments on the Rock Types Reported:
These rock names were reported for the occurrence area by numerous workers. The names have been somewhat simplified – there are many varieties of most of the types.

Giles Peatfield
BASc. (Geological Engineering) University of British Columbia 1966.
PhD Queen's University at Kingston 1978.
Worked for Texas Gulf Sulphur / Texasgulf Inc. / Kidd Creek Mines - 1966 to 1985.
Consultant 1985 to 2016

Other Databases

Link to British Columbia Minfile:	094C 034

References