How Diamonds First Came About
Mined diamonds, also known as natural diamonds, are formed deep within the Earth’s mantle over billions of years under high pressure and temperature conditions. They are brought to the Earth’s surface through volcanic eruptions in rock formations called kimberlites or lamproites. Mined diamonds are the traditional and historical source of diamonds and have been used in jewellery.
One of the key attributes of mined diamonds is their rarity. Large, high-clarity diamonds are relatively scarce in nature, which contributes to their value. The diamond mining process involves extensive exploration, extraction, and processing efforts, making it a labour-intensive and costly venture. Mined diamonds have been deeply ingrained in human culture, symbolising love, commitment, and luxury. This strong cultural association has further driven their demand and value in the global market.
However, advancements in technology have given rise to new methods of diamond production, namely High Pressure High Temperature (HPHT) and Chemical Vapor Deposition (CVD).
In this blog post, we will explore the fascinating differences between HPHT and CVD diamonds, shedding light on their unique manufacturing processes, properties, and their impact on the diamond industry.
Understanding HPHT Diamonds
HPHT diamonds, short for High Pressure High Temperature diamonds, are created by simulating the conditions found deep within the Earth’s mantle. This process mimics the natural formation of diamonds over millions of years. Here’s a breakdown of the key features of HPHT diamonds:
- Manufacturing Process: HPHT diamonds are created by subjecting diamond seed crystals to intense pressure and high temperatures. The process involves placing the seed crystals in a diamond press and subjecting them to pressures ranging from 5 to 7 GigaPascals and temperatures around 1,300 to 2,500 degrees Celsius. Carbon-rich materials act as the source of carbon, which ultimately crystallises to form the diamond.
- Colour Enhancement: One of the notable features of HPHT diamonds is their ability to alter the diamond’s colour. During the HPHT process, certain elements, such as nitrogen, can be removed or added to modify the diamond’s hue. This allows manufacturers to produce fancy coloured diamonds more economically.
- Natural Diamond Composition: HPHT diamonds have the same chemical composition and crystal structure as natural diamonds. They possess exceptional hardness, brilliance, and durability, making them virtually indistinguishable from their mined counterparts.
Understanding CVD Diamonds
CVD diamonds, or Chemical Vapor Deposition diamonds, represent another ground-breaking technique for diamond synthesis. This process involves the use of chemical reactions to grow diamonds layer by layer. Let’s delve into the unique aspects of CVD diamonds:
- Manufacturing Process: CVD diamonds are created through a chemical process in a controlled environment. A small diamond seed crystal is placed in a sealed chamber, and a carbon-rich gas (such as methane) is introduced. The gas is then ionised, breaking down its molecules and depositing carbon atoms onto the seed crystal. This deposition continues layer by layer, resulting in the growth of a larger diamond.
- Enhanced Purity Control: CVD diamonds offer excellent control over purity and clarity due to the precise chemical reactions involved in their formation. This enables manufacturers to produce diamonds with exceptional clarity, minimizing the presence of inclusions and impurities.
- Versatile Applications: The controlled growth process of CVD diamonds allows for the production of large, high-quality diamonds with relative ease. This versatility has led to their use in various industries beyond jewellery, including electronics, optics, and cutting tools.
Comparing HPHT and CVD Diamonds
While both HPHT and CVD diamonds offer alternatives to mined diamonds, there are notable differences between them:
- Manufacturing Complexity: HPHT diamonds require high-pressure machinery and extreme temperatures to create conditions similar to those found deep within the Earth. CVD diamonds, on the other hand, rely on controlled chemical reactions, which can be performed in specialised growth chambers.
- Colour Manipulation: HPHT diamonds have the advantage when it comes to colour enhancement. The process allows for the alteration of diamond colour through the addition or removal of certain elements. CVD diamonds, while typically colourless or near-colourless, lack the ability to modify their colour in the same manner.
- Purity and Clarity: CVD diamonds often exhibit exceptional clarity due to the precise control over impurities during the growth process. HPHT diamonds may contain inclusions, although they are typically
Another useful source to learn more about lab-grown diamonds is the Gemological Institute of America. Read more on the GIA website, here.
