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What’s the Difference Between Diamonds and Other Gemstones?

28 July 2017
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Both diamonds and gemstones are crystals of certain elements or compounds, but what’s the difference between coloured diamonds & other gemstones?

When we think about engagement rings and jewellery, the most popular stone  to go with the precious metal of choice is a brilliant white diamond. At Diamond Heaven, we love diamonds (it's in our name after all). From shining black diamonds to sparkling yellow and even pale pink, diamonds are forever. Choosing to have a coloured diamond on your engagement ring or pendant might seem like a bizarre choice - especially when there are so many gorgeous gemstones to choose from out there. From beads of Jade for beauty, to dazzling blue Sapphires to a deep red Rubies, the intense colours of gemstones can transform a piece of jewellery - so why should you choose coloured diamonds such as a black or yellow diamond over them? Aside from the price tag of a coloured diamond, how do they compare to other gemstones? We thought we'd have a look into it!


Where are Gemstones and Diamonds formed?

First things first, diamonds fall under the category of gemstones, and this is because all gemstones are crystals formed from certain compounds or elements. Alongside this, gemstones are rare and made naturally. This means that rubies, emeralds, sapphires, diamonds and so on are created in rocks found in the earth's crust, roughly three to 25 miles beneath the earth's surface. However, diamonds are formed much deeper in the Earth's surface.


Which rocks are Gemstones formed in?

The earth's crust is made up of three different kinds of rock; igneous, sedimentary and metamorphic.  


Igneous Rock

Igneous rock (also known as kimberlite) can be formed two different ways;

  • The cooling and crystallization of magma beneath the earth's surface (intrusive or plutonic).

or

  • Lava flowing to the earth's surface (extrusive or volcanic).

How are Gemstones formed in Igneous Rock?

Interlinking crystals grow within intrusive igneous rock, sometimes forming gemstones depending on the following three factors;

  • Elements present,

  • Cooling time,

  • The environment.

In deeper environments, the slower cooling the larger the gemstone is.

To form a gemstone or crystal, the Kimberlite originates from the Earth's mantle (>125 miles) and stops at the Earth's surface.  Molten magma with temperatures between 700 °C to 1300 °C runs through the kimberlite and then reaches the surface as lava. If the magma doesn't reach the surface, it cools more slowly, crystallising and forming coarse-grained minerals. Gemstones found in igneous rock include the following;

  • Amethyst,

  • Citrine,

  • Ametrine,

  • Moonstone,

  • Diamond,

  • Tanzanite,

  • Topaz, Zircon.


Sedimentary Rock

Sedimentary Rock is a rock formed by the deposition and successive cementation of the material at the Earth's surface within bodies of water. Sedimentation is the collective name for the processes that causes mineral and/or organic particles  to settle in place.

How are Gemstones formed in Sedimentary Rock?

Sedimentary gemstone happens when water mixes with minerals on the Earth's surface. Rock is worn down, and fragments of mineral rich water and wind seeps down into the cracks and cavities in the Earth's surface, depositing layers of minerals which are then compressed over time, forming gemstones.  Gemstones found in Sedimentary Rock include:

  • Opal,

  • Zircon,

  • Jasper,

  • Malachite.


Metamorphic Rock

Metamorphic Rock is formed when intense underground heat and/or pressure changes rocks that are already there.

How are Gemstones formed in Metamorphic Rock?

Metamorphic refers to the circumstances where heat and pressure change pre-existing minerals into something new. This means that the underground pressure forces minerals and elements that are already there to form into beryls. These gemstones include:

  • Emerald,

  • Aquamarine,

  • Jade,

  • Ruby,

  • Zircon.


The formation of a Diamond vs A Gemstone

One of the most significant differences between diamonds and other gemstones sits within the formation of a diamond. Diamonds are the only gem formed from a single element - highly pressurised carbon. All other gems are compounds of two or more elements. For example, sapphires are a variety of the mineral corundum, an aluminium oxide. The sapphire's intense colour comes from traces of elements such as iron, titanium, chromium, copper, or magnesium.


Why do Diamonds Cost more Than other Gemstones?

Another notable difference between diamonds and other gemstones is the considerable price difference. Gemstones respond to normal market pressures - the prices go up and down with demand and supply, but this is not the case for diamonds. There is a monopoly on the price of diamonds, as they are held artificially high by a single company. Huge amounts of diamonds are also in storage in order to create a shortage and so keep the price up. This price manipulation is allowed in diamonds but prohibited for other gems and precious metals.


Is a Diamond Precious or Semi-Precious?

The categories precious and semi-precious are 19th century terms that were coined in order to designate the value, beauty, rarity and popularity to gemstones. Gemstones have been known to switch between categories, such as the Amethyst, which was considered a precious stone until large deposits of the stone were discovered in South America during the 1800's. At present, there are only four jewels considered to be precious stones:

  • Sapphire,

  • Emerald,

  • Diamond,

  • Ruby.


Are Diamonds Naturally Clear?

The purity and value of a diamond is measured by the 4 C's - clarity, cut, colour and carat - you can find out more about that here. When a diamond is formed, it is rare that they occur in the colourless and perfectly clear aesthetic we're so used to seeing. Diamonds come in a variety of colours due to interstitial impurities and structural defects that cause this colouration. Diamonds are formed in a plethora of colours, from gray to white, blue, yellow (the most common), orange, red, green, pink to purple, brown, and black. The deeper the colour of the diamond, the rarer the diamond is. Whilst some coloured diamonds are considered to have interstitial impurities or structural defects, they're still just as beautiful and enduring as a clear diamond. Alongside this, diamonds are indisputably tougher than any other type of gemstone, therefore having a longer life span.


Do you prefer coloured diamonds or gemstones? Let us know in the comments!