How Diamonds Form: Explaining the Science of their Development
Rough Natural Diamonds
Diamonds are carbon-based minerals that form over the course of a long period of time (millions to billions of years) primarily within the Earth’s mantle. How and for what reasons these precious stones that most consider a luxurious resource form has been the fascination of scientists for many a year, and no doubt would have held the fascination of the thinkers and curious souls of ancient times. In the ancient world of the Greeks, diamonds were believed to be the tears of the gods, with the origins story of Apollo and Artemis being a source of inspiration for this belief. Things have certainly changed today in our pursuit of understanding when it comes to the origin of diamonds, and most other natural phenomena. Diamonds are precious stones that are valued for their rarity, beauty and durability. The question is how did such a thing of value come into being? Naturally. Since we are not talking about artificial or lab-grown diamonds, which is a discussion for another time. When it comes to diamonds it is important that we start by understanding their basic character, for, despite their apparent simplicity, diamonds are the product of complex processes.
Are Diamonds Hardened Carbon or a Variant of Coal?
To start with the basics, diamonds are carbon-based substance. Carbon is one of the most abundant minerals on Earth, and given its abundance, it is a bit of a mystery why there aren’t more of them around (But who knows maybe there is, and we just don’t know). One of the reasons for the rarity of diamonds is the process of their formation. Since diamonds are hardened carbon atoms there’s a tendency to think of them as another variant of coal. This is a point that is worth making since a number of sources online seek to make the case for the difference between diamonds and coal. First, diamonds and coal are both carbon-based substances, with the key difference being the crystal structure of the carbon atoms; a feature that distinguishes another carbon-based substance: graphene. So diamonds are hardened carbon atoms that come with a distinct crystal structure, the question is how did this come into being? A clue is where these substances are found: coal is a mineral that is mined, like diamonds, however, coal is found closer to the Earth’s surface. Diamonds on the other hand are located much deeper. The next key factor is the chemical composition of the mineral, diamonds owe their clarity and hardness to their more unified chemical composition. Coal on the other hand is more varied in its chemical composition, given its origins being the decomposed plants that have broken down into their present state. Diamonds thus can be considered a purer carbon structure.
Diamond Formation Process
Whilst it is impossible to say how exactly diamonds form, that is to pinpoint each and every step of the process, on how these hardened carbon minerals attain their specific state, based on years of observation, scientific research, and more recently with the advances in the study and development of artificial diamonds, key features of this process have been observed. Diamonds are minerals that are found deep underground, usually stretching for hundreds of kilometres (possibly more) into the Earth’s surface. Deep within the Earth’s surface where there is extreme heat and pressure: this is a key factor. Since the hardening of these carbon atoms, which leads to this solid-state requires heat that goes into the thousands of degree of Fahrenheit, combined with hundreds of thousands of pressure. This is important, for these are the same conditions that replicated in labs where diamonds are made artificially.
The Role of Lamproite and Kimberlite in Diamond Formation
If you have in any way be familiar with the widely available literature on how diamonds form online or elsewhere, you are likely to have run into the terms lamproite and kimberlite, and to a lesser extent lamprophyre. What are they, and what role do they play in the formation of diamonds. Let’s start by defining what these technical terms, refers to. Kimberlite and lamproite are igneous rock types: which means these were formed by the solidification of magma, and are found in the shapes of pipes, which is a result of the volcanic process that underlie their development. The differences between these magma types come down to the type of materials contained within them and their differing mineral character. These hardened magma pipes act as “transporters” carrying the diamond gemstone closer up to the surface. These different rock types varying in terms of country and region in terms of their popularity.
Kimberlite gets its name from the Kimberley region in South Africa where the global diamond trade took off. Kimberlite pipes are high in magnesium, carbon dioxide, and water, and today is the primary source of diamond, with the number of discovered pipes (defined as diamondiferous) around the world numbering in the thousands (1). Lamproite rock formation is common in Australia, with the famous Argyle diamond mines being found in a type of this rock olivine lamproite. As noted these various rock types, which and their formation are not the source of diamonds, but rather they are the key sources that carry the precious stones, diamonds in this case, to a more accessible level. Which make them xenocrysts, meaning the carbon-based stones are not part of the magma in which they are found. The volcanic process, which took place over the centuries driving these gemstones that are carried upward via molten magma that cools and solidifies as it reaches the surface.
Triggers that Lead to the Formation of Diamonds
Whilst the factors that lead to the formation of diamonds are generally at the level of principle, the specific interactions that give rise to them are quite varied. The Metasomatic character of diamonds (the formation of minerals via the process of dissolution and replacement of preexisting elements) is an indication of its varied character of their formation:
Heat within the Earth’s Mantle
As noted heat and pressure are the two key factors that cause the formation of diamonds. Deep within the Earth’s surface where these two variables are pervasive, and when the right mineral conditions are met, the process that enables their formation beings. Often taking millions if not more years, as these elements come together, melt, change and solidify.
Deep Level Subduction
Diamonds that form via this process involve plate tectonics, which were movements that take place within Earth’s crust, notably the collisions; often caused by natural phenomena like earthquakes, tsunamis and volcanoes which causes one of the plates to slide beneath the other (2). The research in this area of diamond formation is relatively new, with the advances in measurement techniques and technologies that have enabled the study of the process that leads to the formation of diamonds.
Cosmic Origins of Diamonds
This interesting as it posits the origins of diamonds or at least the process that leads to the process that enables their formation in nature to factors that are from space. Earth over billions of years has been subjected to cosmic strikes from meteors and asteroids. The collisions of these hardened space materials with the Earth’s surface, hitting the ground usually at high heat and pressure sets in motion the formation of diamonds.
References
https://www.sciencedirect.com/topics/earth-and-planetary-sciences/lamproite
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