Flake Graphite and Vein Graphite both form by precipitation of carbon in a high-temperature, high-pressure environment. Sources of the free carbon atoms might be magmatic, thermal decomposition of carbonates, or pyrolysis of organic matter. The free carbon is transported from the source to the location where it precipitates as a crystal. Flake and vein graphite tend to be the purest forms (high grade) and have the best electrical and thermal properties, and therefore command the highest prices. Both types are found at the Ruby Graphite property.

Flake Graphite is found as disseminated crystals in a host rock which is commonly granite, pegmatite, gneiss, schist and on occasion, marble or other metamorphic rock types.

Vein Graphite forms by the same mechanism as flake graphite, but the precipitation occurs within open fissures, fractures, vugs or other spaces within the host rock, resulting in massive crystal bodies ranging from thin individual veinlets to thick pods to stockwork-type vein groups. Disseminate flake graphite is often found in the host rock surrounding vein graphite.

Amorphous Graphite is a micro-crystalline form and is the result of in-place metamorphism of organic material such as a coal seam or carbonaceous shale. North American examples of amorphous graphite are the small occurrences in New England and the large deposit in Sonora, Mexico. Amorphous graphite is the least pure form, having the highest mineral content, has the poorest electrical properties, has the greatest availability with large production from China, and is therefore the least valuable form of graphite.