Graphite 

This is the mineral Graphite. Note that it’s classified as a Native Element Mineral because it's entirely composed of just one element, Carbon. Graphite has all the characteristics required of minerals. Minerals must be naturally occurring, inorganic solids with distinct chemical compositions and physical properties, as well as an orderly arrangement of atoms within a crystalline lattice. Since Graphite has all these characteristics, it’s rightfully classified as both an element and a mineral. Graphite exhibits basal cleavage, meaning that every cleaving plane runs parallel to other planes. Its specific gravity is about 2.2, making it feel very light in your hand. Graphite has a distinctively shiny, metallic luster and feels greasy and even slippery. When drawn across a white ceramic streak plate, it leaves a very dark black streak. It’s so soft that you can repeat this on a sheet of paper and watch it produce the same black mark. Smearing graphite on paper is possible because it’s so soft, ranking between 1 and 2 on Mohs hardness scale. You have likely smeared graphite across paper, because this mineral is used in pencils where it’s mistakenly called Lead. Graphite is commonly used as a dry lubricant. You can pick some up at your local hardware store if you ever need to lubricate a sticky lock or squeaky door hinges. There are many industrial applications for Graphite, including steel manufacturing and electrode production. It’s also a common mineral used to create brake linings and lithium-ion batteries.