Graphite

Chemical composition: The chemical composition of natural graphite is carbon (C), and it often contains impurities such as SiO₂, Al₂O₃, FeO, CaO, etc. These impurities exist in the form of quartz, pyrite, carbonate, etc.

Physical properties:

Appearance: Natural graphite minerals are iron black or steel gray in color, with a bright black luster on the streak, and have a metallic luster. The cryptocrystalline aggregates have a dim luster and are opaque.

Hardness: The Mohs hardness is 1-2, the vertical cleavage plane is 3-5, the parallel cleavage plane is 1-2, it is soft, has a slippery feel, and is prone to contaminating fingers.

Density: The density is 2.09-2.23 g/cm³, the theoretical density is 2.26 g/cm³.

Specific surface area: It ranges from 1 to 20 m²/g.

Melting point and boiling point: Under oxygen-free conditions, the melting point is above 3000°C, and the boiling point reaches 4250°C. It is one of the most heat-resistant minerals.

Structural characteristics:

The crystal of natural graphite belongs to the complex hexagonal double cone crystal type, presenting hexagonal plate-shaped crystals. Common crystal forms include parallel double faces, hexagonal double cones, and hexagonal columns. However, well-formed crystal forms are rare, and it is generally in the form of flake or plate, and the aggregates are in the form of dense blocks, soil-like or spherical.

In the layered structure of graphite, carbon atoms form σ bonds with sp² hybrid orbitals and use the remaining p orbital to form delocalized π bonds. Electrons can freely move in the lattice, giving graphite electrical conductivity and thermal conductivity.