Properties and Thermodynamics
- Diamond is a solid form of pure carbon with a diamond cubic crystal structure.
- It has the highest hardness, thermal conductivity, and refractive index of any natural material.
- Most natural diamonds have ages between 1 billion and 3.5 billion years.
- Synthetic diamonds can be grown from high-purity carbon under high pressures and temperatures.
- The equilibrium pressure and temperature conditions for the transition between graphite and diamond are well established.
- Diamond is metastable at normal temperature and pressure, with graphite being the stable phase of carbon.
- Rapid conversion of graphite to diamond requires pressures above the equilibrium line.
- The melting point of diamond increases with increasing pressure, but at very high pressures, it decreases.
- Diamond can melt into a metallic fluid at ultrahigh pressures and temperatures.
- The most common crystal structure of diamond is diamond cubic.
- The unit cell of diamond has a length of 3.567 angstroms.
- Diamond cubic lattice can be thought of as two interpenetrating face-centered cubic lattices.
- Diamonds can also form a hexagonal diamond or lonsdaleite structure.
- Diamond can have various crystal habits, including euhedral or rounded octahedra and twinned octahedra.
Main Diamond Producing Countries
- Diamond is a solid form of carbon with high hardness and thermal conductivity.
- Diamond anvil cells can subject materials to high pressures found deep in the Earth.
- Different colors in diamonds are caused by small numbers of defects or impurities.
- Natural, synthetic, and imitation diamonds can be distinguished using optical techniques or thermal conductivity measurements.
Uses and Applications
- Diamond is used in major industrial applications such as cutting and polishing tools.
- It has high thermal conductivity, sound velocity, and low adhesion and friction.
- Diamond's optical transparency extends from the far infrared to the deep ultraviolet, with high optical dispersion.
- Diamond is chemically inert, not reacting with most corrosive substances, and has excellent biological compatibility.
Geology and Exploration
- Diamonds are extremely rare, with concentrations of at most parts per billion in source rock.
- They are found in kimberlites on the oldest part of cratons, as well as in lamproites and lamprophyre rocks.
- Geophysical methods like aeromagnetic surveys and electrical resistivity aid in identifying promising regions for diamond exploration.
- Diamonds are dated using radioactive isotopes, with kimberlite diamonds having ages between 1 and 3.5 billion years.
- Gem-quality diamonds come from depths of 150-250km in the lithosphere, specifically from mantle keels.
Diamond Data Sources