Oct 13

Did you ever look at a beautiful diamond and wonder just how something that began life as a rock mined from the ground ended up a something so precious? The simple fact is that there is a lot more to a diamond than many people realize.

Of all of the precious gemstones in the world, the most prized is the diamond. And with its beautiful sparkle and gorgeous clarity that is hardly a surprise. Yet, in reality, all a diamond really is a form of carbon, an element so common that it makes up 18% of the average human’s body.

The Three Forms of Carbon

Carbon, in its solid form, manifests itself in nature in three different ways:

GraphiteGraphite – A rather soft, black colored mineral that is formed out of pure carbon. Its molecular structure is not as dense or compact as a diamond’s, which is why it is so much weaker than it.




fulleriteFullerite – A mineral that is made up of totally spherical molecules made up of exactly 60 carbon atoms. This allotrope – form –  of carbon was not actually discovered until 1990.




uncut diamondDiamond – a very hard, clear crystal.

Contrary to popular belief, coal is not a pure allotrope of carbon. It is, instead, dead vegetation that over the course of thousands of years was fossilized by a process that is known as ‘carbonization’, thus the confusion.


How Diamonds are Formed

Diamond earth layersDiamonds form deep within the Earth, within the molten core of the planet’s mantle. Here, the conditions are just right for carbon to be transformed into diamond. In order for this to happen a perfect synergy must occur; carbon must be under at least 435,113 pounds per square inch of pressure at a temperature of at least 752 degrees Fahrenheit. These conditions exist in the planet’s mantle. At higher levels in the planet’s core these values drop and carbon becomes graphite instead.


Most of the diamonds that are mined today are millions of years old. They were forced closer to the surface of the planet by volcanic eruptions, eruptions that created what are called Kimberlite pipes. They were given this name because the first discoveries of such things were made in Kimberly, South Africa.

diamond pipe These pipes were formed as magma flowed through deep cracks in the Earth. This magma forced the diamonds upwards, along with debris, towards the surface. These episodes were brief, lasting, scientists believe, for just a few hours, but were far more powerful than any volcanic eruption that might occur today.


Over the centuries, the magma cooled. As it did so, layers of rock formed within the pipes, rock that was full of diamonds. When miners are searching for diamond deposits it is kimberlite, which is a pale, bluish rock, that they are looking for.


Diamonds are also occasionally found in riverbeds. These diamonds came from the kimberlite pipes like any others, but were then shifted and displaced by geographical shifts. Some glaciers and other bodies of water have ‘moved’ diamonds thousands of miles away from the location where they originally surfaced from the planet’s core. These days, most of the world’s ‘diamond stock’ is located in in South Africa and a number of other countries on the African continent, as well as in lesser numbers in Brazil and Australia.


Diamond’s Special Properties

Obviously, a cut diamond is a truly beautiful sight to behold, but what is it about them, in terms of structure, that makes them so different from other pretty gemstones? Well, to begin with, they are the hardest known mineral on the planet. The Mohs Hardness Scale is a  scientific reporting scale, devised by mineralogist Friedrich Mohs to measure the hardness of various minerals. You can see how a diamond stacks up in the chart below:



It is their molecular structure that makes diamonds so hard. Diamonds are made up of atoms of carbon that are linked in a kind of lattice type structure.  Each one shares electrons with four others, forming a tetrahedral unit, which is a very strong molecule. The other very common form of solid carbon, graphite, is not as tough because its atoms are linked as rings, creating a much weaker bond.


From a Rock to a Gem

diamond2_kimberliteWhen a diamond is mined, it is a part of the kimberlite rock. Once it is separated, it has to be carefully examined. Only about half of the diamonds mined in the world have the potential to become fine gemstones. The lesser quality diamonds do not go to waste though, they are used in industrial applications in which a hard, precise cutting edge is required.


Gemstone quality diamonds then go through a process that can take anywhere from several hours to several months to complete, during which the actual stone itself may lose up to half of its original weight!


The methods used to do this are delicate and call for a great deal of skill. These days the following techniques are used to do this.


Cleaving – Cleaving is used to reduce an uncut diamond to a size that is more workable. The diamond is cleaved along its tetrahedral plane. This is executed by using a mold – usually one made from wax or clay, to hold the diamond steady while a sharp groove is cut along the length of the plane. This new groove is then used to cut the diamond in half.

Sawing – Cleaving is not suitable for all diamonds. If no plane of weakness can be found within the diamond it must be sawn instead.  This is done using either a very precise laser or a bronze blade that is being rotated at very high speeds. In this case it is up to the person cutting the diamond to determine how it will look after it is cut.

Cutting – Cutting determines the final shape of the diamond. These days, this can be diamond-cutperformed either by hand or using a specialist machine. Either way, diamonds are used to cut diamonds, which is of course logical as it is such a hard mineral.

Polishing – This final step creates the beautiful ‘sparkler’ that can then be incorporated into a piece of fine jewelry. To polish a diamond it is placed on an arm above a polishing wheel that is rotating at a high speed.  The wheel itself is coated with diamond dust, which is very abrasive, that will smooth the surface of the diamond as it presses against the wheel.


Understanding the Four ‘C’s

Even if you have never purchased a diamond before you have probably heard that the quality and value of a diamond is judged by the fours ‘c’s – cut, clarity, carat and color. But what exactly does that mean?

Cut – Diamond can be cut in many ways and because doing so is something of an art not all diamonds are considered to be cut to the same standard.

Clarity – This term is a measurement of an individual diamond’s flaws, or inclusions. Accepted clarity levels start with Flawless and then descend in the following way;very very Slight (VVS), very slight (VS) and slightly included (SI).

Carat – The weight of the diamond. 1 carat is equivalent to about 200 milligrams.

colored diamondsColor – In reference to transparent diamonds, the color scale goes from D to Z, starting off with Icy White — the usual color of the most prized transparent diamonds  — and ending with a light yellow. It should be noted that not all diamonds are transparent; there are blue, black, red, green, violet and pink diamonds. These naturally colored gems are rarer though, and can be very expensive indeed.

And there you have it, the story of the journey each diamond must take in order for it to become part of a fabulous piece of fine jewelry. We bet you never imagined it could be quite so complicated!

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2 Responses to How Diamonds are Formed – The Journey From Common Compound to Precious Gem

  1. Pingback: Precious Rock | rozeworx

  2. Joe says:

    Hi Melanie
    very detailed information on the history of diamonds.

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