Diamonds Term Paper

Introduction
Diamonds are carbon-based rock formed deep in the earth’s mantle at depths of above 150 kilometers. Diamond formation requires extreme pressure and temperature that is only found in the mantle. The ideal temperature and pressure for the formation of diamonds is only found in some zones of the mantle christened diamond stability zones (King, 2015). These zones are thought to exist on the interiors of continental plates where the mantle is relatively stable. Diamonds formed in these zones are then transferred to the earth surface through geological processes (King, 2015). Geologists speculate that most diamonds are formed from carbon compounds that were trapped in the interior of the earth when the planet formed. Most diamonds are thought to have formed during the earth’s formation and remain in the mantle from where they are occasionally thrust to the earth’s surface.

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Most of the retrievable diamonds are formed through four processes. out of these four, one accounts for 99% of all the commercially available diamonds. Diamonds are formed in the diamond stability zone are formed at high temperatures of around 1050°C and 150km below the earth’s surface (Wang et al. 2018). These diamonds may be transferred from the mantle to the earth surface through volcanic eruptions. The eruptions carry parts of the earth’s mantle containing diamonds. The volcanic eruptions form volcanic pipes that are sought by diamond prospectors. These pipes are categorized into lamproite and kimberlite pipes (Wang et al. 2018). Some of diamonds in eruption deposits are eroded by the elements and end up on sediments in rivers and coastlines. Diamonds emanating from volcanic eruptions are very rare and such eruptions have not occurred in modern times.

The second type of diamonds are those formed through subduction. Some diamonds are formed when rocks are subducted into the earth’s mantle during plate tectonic movements. The rocks are then pushed into the earth’s surface through geological processes (Tappert et al. 2005). Diamonds formed through subduction may have been formed at relatively low pressure and temperature of around 80 km and 200°C (Tappert et al. 2005). support for this theory emanates from studies indicating that some diamonds have characteristics consistent with those of ocean crust while others seemed to have been formed in the presence of seawater (Tappert et al. 2005). Oceanic plates are more suited to subduction than continental plates due to their relatively higher density. Most diamonds formed through subduction emanate from carbonate locks such as dolomite and limestone.

The third type of diamonds are formed through impact events where huge asteroids hit the earth surface leading to instantaneous formation of diamonds at high pressure and temperature (Wang et al. 2018). The extreme conditions for diamond formation occur due to the fact that the asteroids may be traveling at high speeds in the range of 15-20 km per second. When such projectiles hit the earth surface, they create conditions that are conducive for the form of diamonds (Wang et al. 2018). This theory is reinforced by findings of diamond crystals near asteroid impact sites such the Meteor Crater in the US and the Popigai Crater in Russia.

The fourth source of diamonds is space. Most meteorites contain small specs of diamonds that are not visible to the human eye (Wang et al. 2018). Scientists estimate that around 3% of the carbon compounds found in meteorites are in the form of nano-diamonds. Scientists speculate that the diamonds found in meteorites are formed through high impact collisions similar to those that occur on impact sites on earth (Wang et al. 2018). These diamonds are too small to be used in industrial applications but are source of diamond used for scientific research.

The 4Cs of diamond
The first C signifies the cut which is the sophistication in the way the rough diamond was cut to the current shape. The cut significantly influences the gem’s sparkle and the valuation of the gem. The second C signifies the color for colorless gems. The general rule is that the value of colorless gems decreases as the amount of color increases as increasing amounts of color signify high amount of impurities (Smith, 2003). The third C signifies clarity and relates to the imperfections such as impurities and lacerations in the gem. Diamond clarity rating range from flawless to slight inclusions. Flawless gems are very rare and attract premium prices. The fourth C signifies Carat and relates to the total weight of a gem (Smith, 2003). One carat equals 20% of a gram. Typically, small diamonds attract lower prices than larger stones if they are of the same quality. The 4Cs helps gem collectors communicate in a universal language when discussing the quality and values of gems (Smith, 2003). The 4Cs were created by the GIA and most sellers brandish GIA certification as proof of quality.

The Percentage of Each Color Found in a Ton of Kimberlite
Kimberlite is a rock type that is most associated with diamonds. Kimberlite is a granite rock that has a dark blue-green hue when fresh but quickly changes to a yellowish-brown color upon exposure to the elements due to oxidation. Kimberlite pipes were originally discovered in south Africa but were later discovered in other parts of the world (Sell, 2014). However, even though kimberlite rocks are abundant globally, only one percent of such rocks contain commercially viable diamonds. Around 80% of the economically viable kimberlite is found in Russia and Sub-Saharan Africa. The quality of diamonds found in kimberlites varies widely (Sell, 2014).

The most valuable deposit is found in south Africa where miners extract around 340 carats from a ton of ore. The second most productive deposit is found in Botswana and produces 120 carats from 100 tons of ore (The World Jewellery Confederation, 2011). Even though diamond mines are rated based on the number of carats per ton of ore, there are some deposits that are prized by prospectors due to their propensity to produce huge gems of high quality (The World Jewellery Confederation, 2011). This is the case with the Letseng deposit in Lesotho that produces 2 carats from 100 tons of ore but has a reputation of producing huge gemstones of high quality. Large and high-quality diamonds are prized by prospectors as they attract premium prices from collectors.

Diamonds are thrust to the earth surface in the form of lamproite and kimberlite rock pipes. However, for the diamond to survive the eruption, it must be thrust through continental cratons. Only 7% of the kimberlites are Archean cratons out of which only one percent yields commercially viable diamond (The World Jewellery Confederation, 2011). Diamond is explored by tracing garnet stones of the pyrope type in kimberlite rocks. The pyrope is then analyzed to determine the amount of chromium (III) oxide contained in the rock (The World Jewellery Confederation, 2011). Garnet rocks with chromium levels of G9 and G10 are considered to have a high probability of containing economically viable quantities of diamond. Since garnets and diamonds have relatively similar levels of hardness, they tend to remain together in the kimberline as it endures geological processes and exposure to different elements.

Only diamonds formed in the diamond stability zone can produce gem-quality diamonds. The other three processes produce diamonds for industrial use (Azina, 2017). Industrial diamonds are low grade white diamonds of differing levels of impurity that are used for practical applications unlike gemstones that are used as ornaments and assets. Industrial diamonds are used as abrasives and as cutters for cutting or drilling through incredibly hard materials (Azina, 2017). Most industrial diamonds occur in the form of grains that are processed for different applications unlike gemstones that are cut and polished to increase their aesthetic value.

Diamond are a popular gemstone due to their superior optical properties. They have a very high luster that enables them to reflect most of the light that fall on their surface (Torres, Garcia & Patron, 2016). It is this quality that enables diamonds to sparkle when light hits the surface at a particular angle. Diamonds also have a high light dispersion quality that enables them to separate light into different color spectrums (Torres, Garcia & Patron, 2016).

Most industrial diamonds lack the sparkle associated with gemstones. Indeed, industrial diamonds resemble gravel or sand used for construction rather than the polished gems found in jewelry stores (Torres, Garcia & Patron, 2016). Industrial diamonds come with all the range of colors associated with gemstones but the color and other unique characteristics do not affect the price during industrial applications (Torres, Garcia & Patron, 2016). However, some industrial diamonds with certain qualities and gem-standard clarity may find their way into the gemstone market if the market demands such gems.

Gemstones are often cut into symmetrical shapes based on meticulous standards so that they may have maximum sparkle at the top. Typically, raw diamonds that cannot be shaped according to the standards set for industrial diamonds are classified as industrial diamonds whose prices are determined by commodity markets (GIA, 2018). The size of industrial diamonds is not of commercial importance as all industrial diamonds have to be processed for various applications. However, the size of a gemstone is an important quality that has the potential to raise its valuation especially if it turns out to have excellent qualities (King et al. 2005).

The source of a gemstone is an important factor in determining its price as jewelers and diamond investors cherish natural stones (King et al. 2005). However, synthetic diamonds are preferred over natural stones in certain applications. Synthetic diamonds are preferred over natural diamonds in the manufacture of drills used in delicate applications such as precise drilling and polishing applications (Zaitsev et al. 2014). Even though synthetic diamonds may contain impurities, that may lower the price of synthetic gems, industrial applications do not mind such minute levels of impurities (Zaitsev et al. 2014).

Colored diamonds comprise just 2% of all diamonds available in the market and attract higher prices than colorless diamonds (Sullivan, 2015). The diamonds that are classified as colored do not contain nitrogen and are classed under type II group (King et al. 2005). Type II has two subgroups of IIa and IIb. Type IIa includes all diamonds that are pink, brown or colorless and comprised of almost entirely of pure carbon (King et al. 2005). This class contains the purest forms of diamond. Type IIb gems contain traces of boron and are blue in color.

Diamond grading according to color is conducted under the grading system developed by the Gem Institute of America (GIA). Type I diamonds are considered to have the normal color expected of diamonds and range from designations D to Z (King et al. 2005). gems assigned the D rating are the clearest while those assigned Z have a brown or light yellow tinge (Blue Nile Inc., 2017). Diamonds with a D rating are the rarest and attract the highest prices. Colored diamonds are not subject to the GIA scale but are instead graded on subjective quality metrics such as the uniformity of the color, hue, color saturation, and tonality (Breeding & Shigley, 2009). These features are then indicated in the description of the gem (King et al. 2005). These diamonds are not subject to the 4Cs that are used on regular diamonds. The lack of standardized metrics makes grading colored diamonds harder than regular diamonds. However, both regular and colored diamonds are graded on the basis of a benchmark stone christened the masterstone.

Gemstone diamonds are classified into two categories of colorless and fancy colored diamonds. The colorless diamonds in grades D-F are the most valuable (Blue Nile Inc., 2017). Prices decline as the gem goes down the scale until Z. the gems in the lower side of the scale tend to have a yellow tinge. Fancy colored gems are graded according to their color and the intensity of the hue (Breeding & Shigley, 2009). The grading is based on the base colors described below and include fancy white which is different from the D category. Due to the multiplicity of the color variations, the grading of colored gems and subsequent valuation is very subjective.

Rarity of Different Sizes of White Diamond
Colored diamonds form when traces of foreign particles get trapped during the crystallization process. Traces of different compounds produce diamonds of different colors and varying color intensities (Fletcher & Patnaude, 2017). Red and brown gems tend to have experienced more pressure in their formation than white diamonds (Fletcher & Patnaude, 2017). Further, all colored diamonds tend to have experienced high-pressure crystallization during formation than white diamonds.

Naturally fancy colored diamonds are very hard to find. Some experts estimate that one fancy colored diamond is discovered for every 10,000 diamonds (Fletcher & Patnaude, 2017). Fancy colored gems come from different parts of the world including Africa, Australia, Asia and south America with each region being associated with a particular color (Fletcher & Patnaude, 2017). Most pink diamonds available on the global market are sourced from the Argyle mine in Australia (Fletcher & Patnaude, 2017). The mine supplies over 90% of the pink diamonds in the market though the pink diamonds comprise less than 0.1% of the mine’s output (Fletcher & Patnaude, 2017). The Argyle mine has a reputation for producing pink diamonds with a strong hue and high-quality gems. It also produces champagne-brown gemstones.

Most orange diamonds are sourced from Africa. The continent also produces a small portion of the green diamonds. South Africa is renowned for producing yellow and blue diamonds. Angola is renowned for producing low grade white diamonds but has been the source of canary or pure yellow and brown diamonds (Nita, Garbossa & Ciuta, 2018). Central Africa has a reputation for producing black and yellow gems. The Democratic Republic of Congo produces huge volumes of low-grade diamond suited for industrial uses. However, it produces small amounts of cognac brown, strong yellow and orange gems (Nita, Garbossa & Ciuta, 2018). Sierra Leone has a reputation for producing significant amounts of gems that account for over 40% of its diamond production.

India has a reputation for producing blue diamonds. Most purple diamonds are sourced from the Siberia region of Russia. Borneo, in Indonesia has a reputation for producing yellow and brown gemstones (Griffin et al. 2001). Most green diamonds are obtained from south America. Brazil has a reputation for producing brown and yellow gems with a strong fluorescence that makes them have a greenish tinge (Karfunkel & Svisero, 1994). Brazil is also renowned for producing rare reds, intense pinks and blue gems.

Red
Red diamonds are a result of the structural flaws that result from the high-pressure environment in which diamonds form (Tappert, 2011). When the gems are still in the earth’s crust, they are subjected to extreme conditions that distort their crystalline structure enabling them to absorb some bands of natural light spectrum that gives them the red tint (Tappert, 2011). Red gems are very rare as the red hue is a variation of the pink diamonds.

Pink
Pink diamonds are a result of the structural flaws that result from the high-pressure environment in which diamonds form (Tappert, 2011). The same mechanism involved in the formation of red gems is also responsible for the formation of pink gems.

Blue
Blue diamonds are the most valuable diamonds and are formed when boron compounds are sucked during the crystallization process (Tappert, 2011). when the boron bonds with the carbon atoms, the red, green and yellow sections of the color spectrum are absorbed.

Green
Green diamonds form when formerly colorless diamonds are exposed to natural radiation. The diamonds absorb natural radiation from soil in the earth’s crust that is responsible for the green tint (Tappert, 2011).

Purple
Purple gems form as a result of lattice distortion that enables the gem to reflect purple light while absorbing the rest of the spectrum (Tappert, 2011). However, anecdotal evidence suggests that purple gems may contain hydrogen that reflects the purple light.

Violet
The same mechanisms responsible for the formation of purple gems is responsible for violet gems.

Orange
Orange gems form when nitrogen atoms are embedded in the gem in such a way that the blue spectrum is absorbed while the orange light is reflected.

Yellow
Most diamonds including industrial grade diamonds have a yellow tinge. Yellow diamonds are formed when nitrogen molecules are trapped during the crystallization of the carbon molecules that form diamond (Tappert, 2011).

Grey
Grey diamonds are a variation of blue diamonds and are formed by the same mechanism responsible for blue diamonds.

Brown
Brown diamonds are a result of the structural flaws that result from the high-pressure environment in which diamonds form (McLeod, 2012).

White
White diamonds are the purest form of naturally occurring diamond and do not contain traceable amounts of impurities. White diamonds under the D classification are the rarest and most expensive gems in the uncolored category (Tappert, 2011). However, their price is lower than that of premium colored or fancy colored diamonds.

Black
Black diamonds are gems that are laden with impurities in the form of graphite and amorphous carbon. The level of graphite in these gems is so high that they appear to be dark (Tappert, 2011). Essentially, black diamonds are not any different from impure whites apart from the fact that they contain graphite as the main impurity.

Famous gemstones
The Blue Hope has an illustrious history of controversy due to the tragedies that met its former owners but is not displayed at the Smithsonian Institute (Diamond Trade, 2018).

The yellow diamonds from Sierra Leone Zimmi mine are so unique that they are now assigned as a separate category by collectors (Diamond Trade, 2018). The gems feature an intense yellow tint that is unique among yellow gems. They Zimmi yellows attract up to twice the price of regular yellows.

The Cullinan is the largest diamond ever discovered and weighed 3,106 carats. It produced nine large gems and 96 small gems (Diamond Trade, 2018). The Star of Africa is the largest of the gems cut from the Cullinan and is the world’s largest cut gemstone.

Conclusion
Diamond is a naturally occurring mineral that is mined for its industrial and aesthetic uses. Diamond is formed under extreme conditions in the earth’s mantle but is thrust to the surface through volcanic eruptions along Kimberly pipes. Industrial diamonds have little quality requirements while gemstones undergo rigorous embellishment and assessment in order to enter the jewelry market. white gemstones along with fancy colored gemstones are the rarest and most valuable gemstones.

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