Flake graphite occurs as isolated, flat, plate-like particles with either hexagonal or angular edges. It is found in metamorphic rocks — such as limestone, gneiss and schist — either uniformly distributed through the body of the ore or in concentrated, lens-shaped pockets.

Today, flake graphite is the type of graphite that those in the industry are most interested in. That’s because it’s the type of graphite that Tesla Motors (NASDAQ:TSLA) will require for its lithium-ion battery gigafactory; other companies with megafactories in the works will also need it.

Flake graphite comes in four basic sizes: jumbo, large, medium and fine. And while it can be tough to understand how they differ and how they relate to purity, it’s important for graphite-focused investors to get a handle on those topics.

According to Stephen Riddle, CEO of privately owned Asbury Carbons, a supplier of carbon and graphite products for various industrial applications, industry standards for flake size are as follows:

• Jumbo flake: +35 mesh or +500 microns
• Large flake: -35 mesh by 50 mesh or -300 microns by 500 microns
• Medium flake: -50 mesh by 80 mesh or -150 microns by 300 microns
• Fine flake: -80 mesh and finer

Speaking to the Investing News Network (INN), Riddle said that when those in the graphite space refer to “good” flake size, they’re usually referring to “a graphite deposit or graphite mine [that] is projected to have a high percentage of its total graphite concentrate with flakes greater than 80 mesh — and preferably including some +50 mesh and even possibly some +35 mesh.”

He added that it’s important to consider whether a company has reached those numbers after flotation “because a lot of times during flotation graphite mines break down the flakes in order to get the purity level required by the market.”

In terms of how purity fits into the mix, Riddle said that in general, “the higher the purity of the graphite concentrate, the higher the average realistic FOB mine selling price tends to be.” Essentially, a purer product will likely require less processing, and thus will cost the producer less money to make.

Overall, then, it would appear that large-flake, high-purity graphite is the most desirable product for a company to have. However, Andrew Miller of Benchmark Mineral Intelligence has explained that the equation is not always that simple. “Quite often because of the niche requirements of each industry … they have very specific criteria. For some industries purity is more important, and for other industries flake size is more important,” he told INN.

For instance, for the spherical graphite industry “purity and the shape of the particle are both key factors.” Meanwhile, for the refractories industry flake size is the overriding price influencer. “It’s not … clear cut,” Miller noted. “There’s no exact perfect grade out there — but there’s a need to tailor what you produce for the market.”

Uses

As mentioned, Tesla and other companies are expected to require large amounts of flake graphite for their lithium-ion battery megafactories. That’s because flake graphite is an important component of lithium-ion battery anodes.

Currently there’s no telling exactly how much graphite these companies may require. Though Tesla has now signed two lithium supply deals, it has yet to secure graphite supply; data on the other megafactories is also scarce.

That said, predictions have definitely been made about how much graphite Tesla’s gigafactoy will require. For instance, Benchmark Mineral Intelligence has said that if it reaches its target capacity of 35 GWh by 2020, it may need 25,000 tonnes per year of lithium, 112,500 tonnes per year of flake graphite, 45,000 tonnes per year of spherical graphite and 7,000 tonnes per year of cobalt.

However, it’s important for investors to remember that flake graphite has applications other than lithium-ion batteries. For instance, fuel cells use even more graphite than lithium-ion batteries, and some expect them to replace combustion engines as a more efficient means of converting fuel to energy. Fuel cells of all sizes are also making their way into the personal electronics sector and even into the utilities sector, where they can be used to provide emergency power to hospitals or turn methane gas into electricity at wastewater plants.

Flake graphite is also an essential part of vanadium-redox battery technology, with nearly 300 tonnes of flake graphite required per 1,000 megawatts of storage. The unique properties of vanadium and graphite combined allow for the long-term storage of excess energy.

Pebble-bed nuclear reactors, which use uranium embedded in fist-sized graphite balls, are another example of how important graphite is becoming to the energy sector. Just one 100-GW pebble-bed nuclear reactor requires 300 tonnes of graphite to start initial production, followed by an additional 60 to 100 tonnes per year for continual operation.