Graphite from the Grenville province in southeast Ontario, Canada

an industrial mineral resource

graphite ore [454 kb]

Fig. 1: Sample 2210, a graphitic marble from the Kirkham graphite deposit, located at the northeast end of Desert Lake in Bedford township, Frontenac county, southeast Ontario. Sample collected loose on 16 November 2000, from extensive dumps generated by a then-recent graphite exploration adit, the entrance to which was sealed. Large sample, 17x11x10 cm, a dull grey crudely banded rock composed largely of fgr crystalline calcite and soft flake graphite. A close look with a hand lens reveals the rock to have a typical grain size of 2-3 mm. Hefting the sample immediately reveals a greasy feel from the soft graphite, which shines on the perfect cleavage planes. The other common mineral is rhombohedral white calcite. Pale (calcite-rich and graphite-poor) bands also display vitreous crystals of pale grey quartz.

"Rock of the Month # 276, posted for June 2024" ---

Graphite in the Grenville province

Graphite is a stable allotrope of carbon, and so a native element, a form of native carbon (a cousin is the more famous polymorph, diamond). It is an important industrial mineral. It has long been used as a lubricant, in pencil "lead", and to fabricate crucibles, but graphite is especially noted for its electrical properties, a function of its remarkable sheet-like structure, and may see explosive growth in demand for uses in batteries. There is a lot of graphite in the Grenville province in North America, notably in the jurisdictions of Quebec, southeast Ontario and upstate New York. Over the last 30-plus years there has been rising interest in graphite as a mineable commodity, especially in Quebec, which has a particularly wide selection of known graphite deposits.

Graphite was long since noted as a component of Grenville marbles, in, e.g., New Jersey (Blake, 1852) and the Adirondacks (Kemp, 1898). It has a well-etablished status as an industrial mineral in, e.g., Canada (Cirkel, 1907), Ontario (Adams and Barlow, 1910), and the Adirondacks (Alling, 1917). It has long been recognized a strategic mineral, often an imported commodity (e.g., back in 1916, >70 percent of U.S. consumption was met by imports from Sri Lanka: Alling, 1917). At one point the former, long-since-flooded Black Donald mine was a major Ontario supplier, and the Kirkham deposit was known even then (Goudge et al., 1957) Deposits in Ontario occur throughout the Grenville province, in the Kingston area, the Ottawa valley, and west of Algonquin park.

Some graphite deposits in Ontario and Quebec

Caveat: Mineral resources have a habit of growing during drilling, but then they may wax and wane, depending on economic factors as much or more than geological definitions, such as mineable width, mining method and cut-off grades, which rest upon fluctuating commodity prices. There are specific definitions of resources and reserves (the latter implying a higher degree of confidence, the delineation of which is an art involving both geological knowledge and statistical expertise. Cutting the resource to a smaller area of higher-grade zones will increase the grade, but ultimately may not be mineable. The head grade in the mill may vary by an order of magnitude, 2-20% graphite. The numbers quoted here should not be considered comparable, nor up-to-date, nor precisely specified, but taken together they give an indication of the sizes of graphite deposits.

Ontario: The Kirkham deposit, 40 km north of the city of Kingston, is well-regarded for flake graphite, and was often in the news from the mid-1980s onwards. Graphitic carbon was assayed in drill core obtained by following an electromagnetic conductor on the property (Anon, 1987a). Geophysical surveying identified several conductive horizons. The drilling at the time informed a resource estimate of 4 million tonnes grading 7% graphitic carbon (Anon, 1987b). A revised estimate of mineable reserves (see caveat above) was 0.85 MT grading 8.6% graphite (Scott, 1990). Black and MacKinnon (1988) and MacKinnon and Baron (1992) reviewed graphite occurrences in southeast Ontario. In 1992, of six major graphite occurrences in the Frontenac axis, four were undergoing active exploration, the target being flake graphite disseminated in marble. At that time, reserves and grades for the Kirkham deposit (zones 1 and 2) were quoted at 1.63 MT grading 9.49% graphite, based on a cut-off grade of 5% C over a minimum thickness of 4 feet (1.22 metres).

Queen's University, in nearby Kingston, has a rather wonderful, quirky set of exhibits in the Miller Museum, housed in the building of the Department of Geological Sciences and Geological Engineering, at 36 Union Street. I last made a series of visits to the display in 2017, and for me a highlight was a marvellous old cabinet on graphite (Fig. 2), showing graphite ore from the old Black Donald mine, a unique graphite elephant sculpture from the Morgan Crucible Company of London, and other graphite samples and artefacts, both natural and synthetic.

graphite museum display [320 kb]

Fig. 2: Display at the Miller Museum of Queen's University in Kingston, Ontario, as noted in the text.

Quebec contains a great swathe of Grenville terrain, and locally very high metamorphic grades. The high-grade terrain contains a significant number of industrial mineral resources, including graphite. Three decades ago, the resource at Stratmin's Lac-des-Iles mine, 22 km south of Mont-Laurier, was quoted as about 21 MT grading 7.5% graphite (Scott, 1990). The Lac Knife graphite deposit 30 km south of Fermont has reserves around 8.1 MT grading 16.7% graphitic carbon - impressive for a discovery made at a solitary showing 1 m2 in size (Bonneau and Raby, 1990)! Located in Grenville terrain, the deposit may be derived from older protolith, the southern extension of the Menihek Formation of the mid-Proterozoic Churchill province. The graphite in the ore is disseminated at grades <10%, forms blebs of increasing size at 10% and higher, and occurs as veins and massive zones at >25%. The ore contains traces of sulphides (pyrite and pyrrhotite) and analyses of ash from graphite reveal some REE, and Mo and V are the most abundant trace elements. Ten years later, Lac Knife had quoted reserves of 5.5 MT grading an average 17.1% carbon, the deposit said to be capable to producing 50,000 tonnes of flake graphite annually, which would make it one of the world's largest producers (Danielson, 2000). Another example, the Matawinie deposit in St. Michel des Saints, has proven and probable metric reserves of 61.7 MT grading 4.23% graphite (Stokes, 2016; Karim, 2022). The La Loutre graphite deposit has current indicated metric resources of 23.2 MT grading 4.51% graphitic C (Northern Miner Staff, 2022). The Lac Gueret deposit has total resources of 62.8 MT grading 17.2% graphitic carbon, with mining plans targeting a small part of that resource for a higher-grade open pit mine with a low stripping ratio (Sylvester, 2018).

Graphite, the mineral and its uses

Graphite, known since ancient times, is newly relevant in the modern world. It is a good mineral with which to complete the 23rd year of "Rock of the Month"! Our host rock this month, graphitic marble, is not particularly common but is reported in, e.g., southeast Ontario, the Adirondack region of upstate New York, in northern British Columbia, and Egypt.

Graphite has long been used as a marker (it is very soft and imparts a grey mark, hence its use in pencils). It is used in crucibles, in refractory bricks and blast furnace linings for the steel industry. Brake linings and brake shoes are another manufacturing use. The mineral has high thermal and electrical conductivity. Its physical properties reflect the crystal structure, with hexagonal rings in planes separated by much weaker chemical bonds. Optical and physical properties of graphite are strongly anisotropic because of the crystal structure, meaning that each property varies, depending on the direction across the crystal in which it is measured. There is increasing use in batteries, where it is an anode material, for both natural and synthetic graphite. This includes lithium ion batteries, one of the major classes of battery planned for the burgeoning electric vehicle market. See also a detailed article in Wikipedia - accessed on 23 February 2024).

As with other industrial mineral commodities, graphite economics is more nuanced than metals, where the amount (first) and the purity (second) lead the price. This is because, depending on the application, suitability of an industrial mineral for a given application may vary not just with purity (always a consideration) but with grain size, crystal shape, colour and other factors. One advantage of graphite for the explorer is that, at least in flake form, it is quite prominent and visually prominent, whether in hand specimen, or under the microscope, where the highly anisotropic flakes are one of the most striking minerals to be seen in both plane- and cross-polarized reflected light. Mines and mills can supply flake, amorphous, vein and synthetic graphites. China, the biggest producer these days, has big resources of amorphous graphite, less of flake graphite. Coarse flake graphite commands a premium with respect to amorphous material.

The market changes with time, as we have seen in dramatic variation (mostly downward) of lithium prices in the past 18 months. China today has become a major influencer of commodity prices, key examples including REE, Li and also graphite. Sri Lanka was noted in the past as a major producer of high-quality vein graphite. Madagascar also contains graphite (and like Sri Lanka and India, was formerly a part of the Gondwanaland supercontinent, with extensive high-grade metamorphic basement, containing pegmatites, gemstones and graphite). Back in 1984, estimated world graphite mine production (all types) was 562,330 tonnes (Borland, 1988). In 2021, this had risen to about 1,034,000 tonnes from mines worldwide. Canada was the 9th largest producer, from one operating mine (Lac des Iles) in Quebec (see Natural Resources Canada - accessed on 22 February 2024). According to NRCan, 2021 global usage of graphite was 3.5 million tonnes, of which was 34% natural graphite and 66% synthetic. China accounted from 79.1% of world mine production in 2021, more than ten times the number 2 producer, Brazil. Turkey, China and Brazil are said to have ther largest known graphite resources. Again, remember there is "graphite and graphite", so the devil is in the details. The various, variably-old resource numbers quoted above do indicate that, when the need arises, Canada has substantial known resources of graphite for mining.


Adams,FD and Barlow,AE (1910) Geology of the Haliburton and Bancroft Areas, Province of Ontario. GSC Memoir 6, 419pp. plus 2 maps.

Alling,HL (1917) The Adirondack graphite deposits. New York State Museum Bull. 199, 150pp.

Anon (1987a) Stewart Lake graphite grade bodes well for production. Northern Miner 73 no.12, 3 (01 June 1987).

Anon (1987b) Graphite producer looks likely for Stewart Lake Resources. Northern Miner 73 no.36, B7 (16 November 1987).

Black,SJ and MacKinnon,A (1988) Major graphite occurrences within the Frontenac Axis, southeastern Ontario. OGS Misc.Pap. 141, 507pp., 359-362.

Blake,WP (1852) Mineralogical notices. Amer.J.Sci. ser.2, 13, 116-117.

Bonneau,J and Raby,R (1990) The Lac Knife graphite deposit. Mining Mag. 163 no.1, 12-18 (July 1990).

Borland,J (1988) Stewart Lake aims at special graphite market. Northern Miner 74 no.16, 1-2 (27 June 1988).

Cirkel,F (1907) Graphite, its Properties, Occurrence, Refining and Uses. Department of Mines, Ottawa, 307pp. plus maps.

Danielson,V (2000) Mazarin's Lac Knife poised to become New Economy mine. Northern Miner 86 no.10, 1,18 (01 May 2000).

Goudge,MF, Haw,VA and Hewitt,DF (editors) (1957) The Geology of Canadian Industrial Mineral Deposits. 6th Commonwealth Mining and Metallurgical Congress, 247pp.

Karim,N (2022) Nouveau Monde feasibility study outlines $1.4B integrated graphite mine and battery plant. Northern Miner 108 no.15, 5 (25 July 2022).

Kemp,JF (1898) Geology of the Lake Placid region. New York State Museum Bull. 5 no.21, 51-67 plus 2 maps.

MacKinnon,A and LeBaron,PS (1992) Graphite occurrences of the Frontenac Axis, Eastern Ontario. OGS Mineral Deposit Circular 33, 31pp. plus map sheet.

Northern Miner Staff (2022) Lomiko Metals aims to be a regional hub to supply the graphite essential to lithium-ion battery manufacturers. Northern Miner 108 no.12, 43 (13 June 2022).

Scott,D (1990) Stratmin, Cal Graphite first of new graphite producers. Northern Miner 76 no.38, 1-2 (26 November 1990).

Stokes,L (2016) Nouveau Monde outlines economics for Matawinie. Northern Miner 102 no.23, 16 (18 July 2016).

Sylvester,B (2018) Mason Graphite's Lac Gueret leads the field in Quebec. Northern Miner 104 no.20, 9-10 (01 October 2018).

Graham Wilson, DRAFT, 19-23,25 February 2024, Figure 2 added 18 April 20224

For further information, see:

Rock of the Month Thematic Index

or, visit the Turnstone "Rock of the Month" Chronological Archives!