Below is a list of Graphite manufacturers from Duluth, Minnesota. Graphite is a naturally occurring allotrope of carbon that can occur in crystalline flakes, amorphous shapes or in lumps of graphite. It is shiny and dark to medium gray in color. Natural graphite is most commonly used to produce lead for use in marking. Graphite can also be synthetically produced in items such as electrodes, rods and tubes; however, it may have slightly different physical properties.