It is difficult to imagine a person who would not have heard of a diamond. Also, everyone knows that diamonds are the hardest, indestructible and rare. We envision a diamond as a colorless or white round brilliant gemstone. Today we want to confirm and refute some theses and open up new facets of a diamond for you. It will turn your idea of this precious stone upside down.
It is a common practice to separate the world of diamonds and colored gemstones. This is because they are so different in terms of formation, mining, enrichment, cutting and refining, and even business model and approach to the industry. Diamond created a separate universe for himself. People who work with diamonds may know nothing about colored stones (emeralds, sapphires, rubies, and tourmalines). The accepted approaches to mining and supply from the diamond industry do not work for colored gemstones.
What is a diamond?
The mineral diamond consists of a single element – carbon, organized in a cubic crystalline structure. Graphite also consists of carbon, as well as graphene and carbon nanotubes, but the carbon atoms in all examples are combined differently. This phenomenon is called allotropy. Diamond and graphite are allotropic modifications of carbon. Therefore, the formation conditions affect whether diamond or graphite will be created from carbon atoms.
The formation of a diamond requires extreme temperature (1150–1200 C) and pressure (50–70 kbar), which occur at a depth of 140–200 km. For comparison, the maximum drilling depth achieved by man is 12 km.
Photo by O. Rybnikova.
Diamond has an incredible brilliance and fire, for which it deserves the primary role in jewelry. Such optical properties are explained by the high refractive index and dispersion.
Diamonds form deep below the surface of the Earth. Minerals reach the surface due to powerful volcanic explosions. Kimberlites and lamproites are rocks that bring diamonds to the surface through volcanic pipes, often referred to as kimberlite pipes.
The hardness and invincibility of a diamond
Diamond is truly the hardest natural substance. This means that the stone can scratch any mineral and metal. But only a diamond can scratch a diamond. However, hardness and toughness should not be confused. A diamond can be easily broken with a hammer. Still, if you try to slowly push the diamond with a hammer, only a dent will remain in the hammer. Also, diamond burns at a temperature of 850 C. This means that a diamond can be crashed and burnt.
It is also interesting that the diamond has its slogan: "Diamonds are forever," invented by the largest diamond mining company – De Beers, at the end of the forties. The advertising campaign had an incredible success. But are diamonds so durable? Eternal? From a scientific point of view, diamond is metastable under the conditions on the Earth's surface. The diamond appeared due to high temperatures and pressures, so normal conditions for us are atypical for it. This does not mean that the diamond will crumble in 10 years. This means that no matter how invincible it is, you still have to treat the stone carefully.
The rarity of a diamond is often built intuitively based on the high price of the stone. But at the same time, any jewelry store sells natural diamonds, but there are no natural emeralds or tanzanite. Also, if you look closely at the diamonds in a piece of jewelry, they will all be the same size and color! Such stones are called calibrated. This means that a lot of material is lost in order to make lots of identical stones (size, proportions, color, clarity, type of cut, weight).
The following question should also be asked: is a diamond rare if there are deposits on every continent (except Antarctica)? At the same time, tanzanite is found in only one deposit in the world. A diamond is rare, but some gems are rarer and cost more.
After all, it may seem that we have dispelled all the praised qualities of a diamond, and it is not so attractive to us now. So here it is, time to talk about the not-so-known facts about the diamond, which will eventually make you appreciate the precious stone even more than before.
Photo by O. Rybnikova.
A diamond has color!
The white or colorless diamonds that we commonly see actually have color too. Most natural diamonds have yellow and brown shades, but they are undesirable and unattractive to industry. Therefore, preference is given to colorless stones. The diamond color scale is standardized. It has 23 degrees and is indicated by the letters from D to Z, where D is colorless, and Z is light yellow, brown, or gray. There is also a separate classification of colored diamonds. They happen to have a Fancy prefix. Colored diamonds can be blue, pink, yellow, orange, green, red, and black. Colors appear due to nitrogen and boron impurities or defects in the crystal structure.
Diamonds and their evaluation are very systematized. For example, the 4C system used for diamond grading describes 4 main properties: color, clarity, carat weight, and cut.
Learn more about the 4C system invented by the Gemological Institute of America (GIA) here.
A diamond from the mantle depths
As mentioned above, extreme temperatures and pressures are necessary to form diamonds. No other colored gemstones demand such extreme conditions. A diamond is formed in the mantle, the Big Three (rubies, sapphires, emeralds), tourmalines, spinels, turquoise, and quartz - in the Earth's crust. It is an incredible success that nature brought diamonds to the surface from the depths of the mantle. Volcanic events of this scale do not occur nowadays. The last explosion was 20 million years ago.
The age of the diamond
A diamond can be much older than the rocks from which it was mined. For example, the age of diamonds mined in Canada is 3.5 billion years. Even though the age of the Earth is 4.56 billion years. Such diamonds are older than life itself on Earth. Incredible, isn't it?
Photo by O. Rybnikova.
There are about 6,000 kimberlite pipes - sources from which diamonds are mined, and only 1,000 of them contain precious stones. At the same time, only 50 kimberlites have diamonds in an amount sufficient for economically profitable mining. But mining is carried out in 20 of them.
Kimberlite pipes are located in ancient areas of the Earth's crust - cratons. Coincidentally, the climatic conditions on their surface (whether the Canadian tundra or African savannas) make diamond mining even more difficult.
Diamonds are truly unique. They were formed at incredible depths, which scientists cannot study directly. Diamonds are millions and billions of years old. To get to jewelry, diamonds went through a complicated path: they withstood a volcanic explosion, were mined from rocks in harsh climatic conditions, and after being cut, they revealed their unique beauty. After all, no matter how expensive bags and clothes luxury brands produce, they will always be made in several copies. At the same time, there are two identical natural diamonds. The multimillion-year history of the mineral is hidden under its brilliant faces.
Rybnikova Olena - gemmologist, MSc in Mineralogy, Geochemistry, and Petrography. Taras Shevchenko National University of Kyiv (Ukraine) alumni. Applied Jewelry Professional certified by Gemological Institute of America. Now she is doing a Ph.D. in Europe and is writing a dissertation on beryllium minerals. Actively popularizes gemstones and gemmology.