Diamond (Carbon allotrope) (C) — Properties, Uses & Safety

Overview

Diamond is a crystalline allotrope of carbon with the chemical formula C and a molar mass of 12.01 g/mol per atom. It is the hardest known natural material, scoring a perfect 10 on the Mohs hardness scale, and possesses extraordinary thermal conductivity, optical transparency, and chemical inertness. In diamond, each carbon atom is sp3-hybridized and covalently bonded to four neighboring carbon atoms in a rigid three-dimensional tetrahedral lattice — a structure known as the diamond cubic crystal system. This extensive network of strong covalent bonds explains diamond's exceptional hardness and extremely high melting point (approximately 3,550 °C at high pressure). Diamond appears as a transparent to colorless crystalline solid, though trace impurities can produce yellow (nitrogen), blue (boron), pink, or green varieties. Natural diamonds form deep within Earth's mantle under extreme pressures (45–60 kilobars) and temperatures (900–1,300 °C), then reach the surface through volcanic eruptions in kimberlite pipes. Beyond their fame as gemstones in jewelry, diamonds have critical industrial applications as cutting tools, drill bits, grinding wheels, and polishing abrasives due to their unmatched hardness. Synthetic diamonds, produced by high-pressure high-temperature (HPHT) or chemical vapor deposition (CVD) methods, now dominate industrial use and are increasingly used in electronics and quantum computing research. Diamond is a superb example for teaching allotropy — comparing it with graphite (sp2-bonded, layered, soft, and electrically conductive) dramatically illustrates how the same element can have vastly different properties depending on its bonding and crystal structure. Diamond also teaches students about covalent network solids, hybridization, band gap theory, and the relationship between atomic structure and macroscopic properties.

IUPAC Name

diamond

CAS Number

7782-40-3

PubChem CID

0

Molecular Formula

C

Molar Mass

12.011 g/mol

State at STP

solid

Appearance

Transparent to colorless crystalline solid