Diamonds are a mineral, a natural crystalline substance, the transparent form of pure carbon or nearly pure carbon. Diamonds have extraordinary qualities. Diamonds have a broad colour range, high refraction, high dispersion of fire, very low reactivity to chemicals, rarity, and of course, extreme hardness and durability. Diamonds are known as the “king of gems” they glitter, dazzle, and symbolize purity and strength.
A diamond is the oldest thing you will ever own, probably 3 billion years in age, fully two thirds the age of the Earth. A diamond is a strategic and high-tech supermaterial for our technological society. Diamond is the birth stone for the month of April.
A diamond is composed of the single element carbon, and it is the arrangement of the C atoms in the lattice that give a diamond its amazing properties. Both diamond and graphite are composed of just carbon. However a diamond is the hardest known material and graphite is one of the softest, this was caused by a rearrangement of the way the atoms are bonded together. Diamond carbon atoms are linked in a regular three-dimensional lattice with a repeating or crystalline pattern.
Diamond belongs to the cubic, or ‘isometric’ crystal system. The most commonly seen crystal structures or arrangements are:
• Octahedron (8 faces)
• Cube (6 faces)
• Dodecahedron (12 faces)
A diamond is the ultimate gemstone, having few weaknesses and many strengths. It is well known that diamonds are the hardest substance found in nature, but few people realize that diamonds are four times harder than the next hardest natural mineral, corundum – sapphires and rubies.
Natural diamonds are formed deep within the Earth’s mantle layer from the element carbon, about 180km below the surface, where high temperatures and pressures exist. Some diamonds form at depths of 300-400 kilometres, or even deeper, but these diamonds are particularly rare.
The earths mantel is made up of molten rock, metals and other materials. The temperature is very high at this depth – between 1100 degC and 1400 degC. The high pressures needed to form diamonds are produced by the weight of 180 km of rocks pressing down. Besides carbon, there are very small amounts of other substances, such as nitrogen and sulfur that can become trapped in the crystal when it is formed in the mantel. These impurities can give color to the diamond. One of the most rare is pink diamonds.
Natural diamonds are classified by the type and level of impurities found within them.
• Type Ia diamond – Most natural diamonds are of this type, which contain up to 0.3% nitrogen.
• Type Ib diamond – Very rare (~0.1%) in nature, but almost all synthetic (industrial) diamonds are of this type. They contain nitrogen at concentrations of up to 500 ppm.
• Type IIa diamond – Very rare in nature, these diamonds contain so little nitrogen that it can’t be easily detected by the usual IR or UV absorption measurements.
• Type IIb diamond – Extremely rare in nature. These have such a low concentration of nitrogen (even lower than type IIa) that the crystal is a p-type semiconductor (due to uncompensated B acceptor impurities).
Due to its unique internal structure and powers of light reflection, when cut to proper proportions, diamonds gather light within itself and then sends it back in a shower of fire and brilliance. The ‘life’ of a polished diamond is regarded as the amount of light that is reflected back to the viewer. The term ‘life’ is also referred to as ‘brilliance’. If the diamond is cut with good proportions then the brilliance will be increased. Lustre refers to the surface gloss on a polished diamond. Fire the play of colours that can be seen from the crown of a polished diamond. As light enters the diamond it is refracted and broken up into the colours of the spectrum and reflected back. The resulting rainbow-like colour flashes are called ‘fire’.
The hardness of diamond is an important property. As an industrial tool it has many uses and modern industry is highly dependent upon it. As a gemstone, it is resistant to scratching and abrasion, which ensures that a finished gem will retain its brilliance and polish. Because of its hardness and the unique way in which it is manufactured, a diamond polishes very slowly. It forms an unusually flat, finely-polished ‘adamantine’ surface, with very sharp, straight edges between facets. No other gemstone can quite match this standard of polish.
Diamond has the highest coefficient of thermal conductivity of any known substance because the closely-packed crystal structure conducts heat very quickly. The thermal conductivity of diamond is five times higher than that of copper. This explains why a diamond feels cold to the touch when first picked up but quickly becomes warm from the heat of your fingers.
Only about one-fifth of all mined diamonds could be considered of gem quality. From 40 to 250 tons of gravel and sand must be processed today to recover one rough diamond from the world’s thinning diamond deposits. Experts estimate that all known supplies of diamonds will be depleted within 30 to 40 years. 75 – 80% of all diamonds mined are used for industrial applications such as drilling, grinding, or sawing. The remainder are used for jewellery or investment. Less than 2% of the diamonds mined are of such high quality that they may be considered investment quality.
On average, 250 tons of ore must be mined and processed to produce a one carat diamond of gem quality. When the mining operation is completed, sorters look at rough diamonds, separating them into small piles by shape, size, and quality, a long and laborious process.
The earliest examples of diamonds in human hands were found 3,000 years ago, in India. There, diamonds were used primarily as talismans to ward off evil and protect the wearer in battle. Diamonds were also used by the early Chinese, Greeks, and Romans as an engraving tool. While there was some mystique surrounding diamonds because they were so rare and difficult to obtain–many early cultures believed they had magical properties
The word “diamond” comes from the Greek word “adamas” meaning unconquerable, in reference to the eternity of love. In 1477, Archduke Maximilian of Austria gave a diamond ring to Mary of Burgundy, thus, starting the tradition of diamond engagement rings. The reason a woman wears an engagement ring on her third finger of her left hand dates back to the Egyptian belief that the vena amoris (vein of love) ran directly from the heart to the top of that finger.
Many of the rarest diamonds occur by rare accidents of nature in shades of pink, blue, green, amber, or even red. These diamonds are referred to as “Fancy” diamonds and are evaluated by a different set of color standards. Fancy diamonds are the most expensive due to their extreme rarity.
Towards the middle of the 20th century, De Beers began using its slogan “a diamond is forever” in its advertising. Their campaign was so successful that today, diamonds are strongly associated with engagement rings–and eternal love.
It is the only gem mineral composed of a single element making it the purest of earth’s gemstones. Therefore it is fitting that the purest and most brilliant of all the world’s gemstones make the diamond engagement ring the perfect symbol of eternal love.