Author: luel.emishaw

Minerals are the building block of planet Earth. They are simply the essential fabric of our existence. For minerals to form you need the ingredients with which you build the minerals (i.e., elements), the right temperature and pressure conditions, space for the minerals to nucleate and grow out into, and time. When minerals are unique in terms of their color, rarity, clarity or have all of these desirable attributes; we call them gemstones.

Gemstones are beautiful, but gemologists have their own objective criteria of defining the most beautiful and desirable gems. In the world of gemology, the color, clarity, size, and cut of minerals determine their desirability. Among the most desirable gem is diamond. Interestingly, it is one of the minerals that was formed following the first supernova explosion. Nature’s arrangement of the bonding of the carbon atoms determines whether we get graphite or diamond. Carbon is the foundation of the organic life and seems to build fascinating wonders in both organic and inorganic worlds. In the Earth’s interior, diamonds are formed at a cratonic keel under immense pressure and temperature. We mine diamonds from kimberlite pipes. Kimberlite pipes are formed due to volcanic activities that bring deep-seated (200 to 300 km) melts and minerals including diamonds, olivine (this is also known as peridot), phlogopites, and carbonates to the uppermost crust. Given the relative rarity of diamonds, our recent capabilities of diamond mass production have been extremely helpful for both the jewelry and manufacturing industry. In 1954, Dr. H. Tracy Hall made the first synthetic diamonds. Dr. Hall was not only a great inventor but also a master of poetic descriptions. When he recollected on his discovery he said, “My hands began to tremble, my heartbeat rapidly, my knees weakened, and no longer gave support.” The GIA Museum in Carlsbad, California has a beautiful display of the diamond press (image below) and Dr. Hall’s discovery story, which also includes the above quote.

Much like diamonds, high-quality rubies, sapphire, and emeralds are highly sought after. From these, ruby and sapphire fall in the corundum group. The vibrant red variety of corundum, which sometimes are also referred to as pigeon blood rubies, command high prices. The red color of ruby is caused by impurities of chromium that substitute for aluminum. Without any impurities, corundum (Al₂O_3, aluminum oxide) is colorless. The vibrant blue variety of corundum is called sapphire. Iron and titanium impurities are responsible for the blue color. Corundum is the second hardest mineral, runner up to the hardest mineral ever discovered, the diamond. Ruby and sapphire are mined from pegmatite bodies and metamorphic terrains. In Asia, it is typical to find rubies within marble.

Emerald is a green variety of the beryl group. Its color is caused by impurities of chromium and vanadium. Emeralds almost always have internal fractures, and they are softer than corundum, but generally quite durable and harder than minerals such as quartz. Emerald is formed in both sedimentary and metamorphic environments. However, the prevalent emeralds are formed in environments where pegmatite intersect with schists. Emerald has a chemical composition that predominantly constitutes beryllium, silicon, aluminum, and oxygen.  

These popular gems are mined all over the world. Diamonds are mined from a few countries in Africa, Canada, Russia, and Australia. From these, if we consider the 2020 global diamond production, nearly 64% of the total production was from Africa. In the chart below, the name of the countries and their respective production are shown.

Rubies and Sapphire are mined from East Africa, Burma (now called Myanmar), Pakistan, Afghanistan, Sri Lanka, and Madagascar. Again, if we consider data published by National Resources Governance Institute (NRGI) in 2017, the ruby production in Africa appears to be higher constituting over 60 % of the total production (chart shown below). Sapphire production is increasing in African countries as opposed to countries like Australia where the trend shows a steady decline. Notably, the supply of sapphire from Asian countries is significant in both quality and quantity.  

Brazil, Zambia, and Colombia are the leading emerald producers (chart shown below). Over half of emeralds production is in Brazil and Colombia. Other countries such as Pakistan, Afghanistan, Israel, China, India, and Ethiopia are among other emerald producing countries.

As the production statistics show, a considerable amount of gemstones are produced in Africa. Africa, as a developing continent, should take advantage of these resources by building gemology knowhow, investing in mining and exploration, and creating cutting facilities. Proper environmental impact studies should be conducted to warrant a hospitable environment during and after mining. Organizations such as the African Union should also be involved in studying the proper economic potential of these resources and implementing continental policies that African countries could benefit from.

The advanced technologies and growing knowledge of mineral formation have created multiple methods of synthesizing gemstones for both commercial and industrial uses. These gemstones are continuously increasing in production for use in both jewelry and industry sectors. Creating alternatives and market interest due to their affordability. However, natural gemstones are still highly sought after and will continue to have prestige and desirability.  

Your friendly geologist, Luel

References

GIA Gem Encyclopedia | Complete List Of Gemstones

7.12: Causes of Color – Geosciences LibreTexts

List of countries by diamond production – Wikipedia

Global-Emerald-and-Ruby-Supply-Analysing-Market-Data.pdf (gemfields.com)

Geology – rocks and minerals (auckland.ac.nz)

Geology considers the immutability of fundamental physical processes across geologic time as one of its principles. This is widely referred to as the principle of uniformitarianism. The principle of uniformitarianism states that the present is the key to the past. Although seemingly simple, this principle has fundamentally revolutionized the science of Geology and considerably modified the philosophical fabric of society by particularly redefining the role of Time in geological processes. For example, uniformitarianism was used to challenge the notion that Earth is only 6000 years old. Simply put, its task is to observe, closely and keenly, the present physical processes in order to infer what might have happened in the past (e.g. examine basins in which sediments are depositing, theorize upon their accumulation and rock formation process, and apply the principles to better understand the formation of sedimentary rocks over millions of years). Accordingly, uniformitarianism accumulates knowledge and insights by starting from particulars and establishing their universals as theories and laws.  

However, like all things with value, uniformitarianism has its own limitations. Bertrand Russel illustrates this limitation eloquently by using his optimistic chicken as an example, “The man who has fed the chicken every day throughout its life at last wrings its neck instead, showing that more refined views as to the uniformity of nature would have been useful to the chicken.” Of course, geologists are well aware of this limitation. They know that the present physical conditions do not necessarily reflect the past physical conditions. For example, our geological findings show that the paleo-climate conditions of the Earth are not the same as our present climate conditions; in fact, it’s been evolving in deep time. Just like the atmosphere, the mineral world has also been evolving, creating new minerals from its predecessors. In general, a whole array of things was way different in the past and interacted differently. These facts but make us wonder whether the utility of uniformitarianism is diminishing.

At face value, it may look like the utility of uniformitarianism is on its last leg. Especially, with the emergence of numerical modeling, and advanced statistical tools including AI. It seems like simulation of the past conditions with a multiple-hypotheses approach may help us better understand the physio-chemical evolution of the Earth better. This is true and more reliant on deductive reasoning. Still, we need a reference for all kinds of numerical and deterministic computations. Uniformitarianism comes, yet again, as the key and not as the exact copy of the past. Secondly, regardless of the nature of reasoning employed, the concept of uniformitarianism should be honored to investigate Earth’s history. In other words, either the present physical processes or the law that governs the physical processes must be considered as immutable for geological investigations to be possible. Despite its limitations, uniformitarianism will continue to serve as one of the pillars of geology. It shall also remind earth scientists that they should always thrive to disprove their hypotheses and the ones they could not disprove, they should accept with a grain of salt.

– Luel, your friendly geologist

Plate tectonics is one of the greatest scientific achievements. It is one of the few scientific blueprints with great predictive and descriptive powers. This single comprehensive theory explains the causes of volcanic eruptions and earthquakes and where we expect them to occur. It tells us from which geologic settings we expect petroliferous, metalliferous, and auriferous deposits. It explains where and how mountains, rifts, and oceans have formed and where we expect these features to form in the future. Plate tectonics is indeed a great showcase of the present scientific strides as well as the driver of the geo-centered economy.

The development of plate tectonics shows that sometimes the scientific conclusions we reach could be counter intuitive. It is not an easy task to imagine and experimentally show the gigantic plates that make up the oceans and continents move over plastic like thick layer of rock called the asthenosphere. But, then to move one step up and say these plates actually move into, away from, and past each other ever so slowly over millions of years creating new oceans, mountains and basins is like discovering a new planet like our own but with unique attributes of its own. This was to geologists what the revelation of time dilation and space contraction of space-time universe was to classical physicists.

What is even more amazing to geologists is the regularity of the process. Without any considerable expansion of the globe, for at least one billion years, Earth has been able to release its heat causing the amalgamation and dispersal of supercontinents through the process of subduction and rift-drift reactions triggered by mantle dynamics. The supercontinent in the recent past being Pangea. For how long would this continue?

Was this process, which is referred to as the Wilson Cycle, unavoidable through the course of Earth’s evolution? What was before plate tectonics and what made this transition possible? Could there be any better comprehensive theory that could explain and predict the geodynamic processes of the Earth better than the theory of plate tectonics? We have much to learn.  

For now, the trend of the geoscientists has been characterizing the processes of plate tectonics in detail by translating the conceptual models of plate tectonics into tectonophysics while expanding the scope of plate tectonics itself. These endeavors are extremely important to predict earthquakes, isolate ideal geo-storage settings, discover resources, and monitor and predict volcanic eruptions, and associated geo-hazards.

We have come a long way from the Earth model that was thought of as resting on the back of four elephants that are resting on the back of a turtle. Beyond all the scientific and material benefits, I think plate tectonics has played a crucial role in redefining our philosophical views through which we view the Earth.

© Authored by Luel Emishaw, Burst of Insights

Humans have been curious about the nature of the atmosphere for thousands of years. However, the effect of this enduring curiosity started to bear meaningful fruit only within the last four hundred years. This mixture of gases that sustained life for billions of years had been elusive to our ancestors. They, of course, did not doubt its existence. The transparency of it did not shadow the chilling breezes, the hurricanes, the tornadoes, the lightings, and the storms it caused. In fact, they moved with it – crossing oceans, seas and straits using boats fueled by winds – and diversified.

For our ancestors, the atmosphere was not just mysterious substances that enveloped the Earth as a blanket. It was rather a magical force of life without which they could not survive, and its god, at least for the Greeks, is none other than Zeus himself, the personification of justice that speaks to thunders and storms. Different civilizations had ways of attributing the undeniable power of the atmosphere to similar mythical gods.

This is an interesting conceptualization, but one that made our ancestors more of stoics and passive and the atmosphere esoteric and unexplorable. Exploring the atmosphere was more like counting the infinite numbers between any two successive Natural numbers, or more like being physically symbiotically cell-close with something that is infinitely foreign to the mind. This recalls what David Wallace Foster once said:

There are these two young fish swimming along, and they happen to meet an older fish swimming the other way, who nods at them and says, “Morning, boys. How’s the water?” And the two young fish swim on for a bit, and then eventually one of them looks over at the other and goes, “What the hell is water?”

Like the young fish in the water, we had been to a certain extent passive to the atmosphere, unable to see it as a mixture of gases that in many ways gave rise to and sustained life. Like the older fish, we needed the same kind of sage, some insightful observers to enlighten us about the air we breathe. Like the older fish that made peace with the water it swims in, the giants among us had to decide and begin at the beginning to study the atmosphere with deceptively simple yet clever methods.

In 1648, Blaise Pascal and Florin Perier collected atmospheric pressure data from Puy-de-Dome using a barometer which was invented by Evangelista Toricelli. Their finding suggests that atmospheric pressure decreases with increasing elevation. Roughly after 139 years, Horace Benedict de Saussure, who was an Earth Scientist by profession, indicated that both atmospheric pressure and temperature decrease with increasing altitude. He collected his data by climbing up to the summit of Mount Blanc. Saussure suffered from altitude sickness and had shortened his expedition as a result.

This continued dream of advancing the frontier of atmospheric science inspired a dangerous and elaborated balloon flight by Henry Coxwell and James Glaisher in 1862. Records show that this might have been the first scientific expedition to make it into the Stratosphere, whose boundary was later identified by Teisserenc de Bort and Richard Assmann in 1902.

In just about 254 years, these great scientists were able to gain important knowledge about the atmosphere that eluded our ancestors for thousands of years. The seed of this major scientific transformation appears to be not taking things for granted, and its continued germination has been supported by the efforts of bright scientists who developed insightful and clever methods to critically examine and discover the remarkable nature of the world around us.

After thousands of years of philosophical speculations and religious assertions, one of the major experimental breakthroughs in atmospheric science was conducted by Joseph Black who released carbon dioxide by burning limestone (calcium carbonate) in 1750. Most importantly, Black was able to reverse engineer this reaction to precipitate out calcium carbonate by bubbling carbon dioxide through a calcium hydroxide solution. This experiment helped him to show that carbon dioxide is present in animal breath, and hence in the atmosphere. Interestingly, he was also able to combine calcium oxide with atmospheric carbon dioxide to form limestone. The original name given to this gas by Black was ‘Fixed air’. Incidentally, calcium hydroxide is formed when calcium oxide (rock formed when limestone is burned at a temperature of 960 °C or higher) mixes with water. This technology was known since ~7000 BCE to ancient civilizations such as the Anatolian civilization, now Turkey.

Following the discovery of carbon dioxide, in 1766, the great experimental scientist Henry Cavendish was able to release the hydrogen gas by combining metal (e.g., zinc) with hydrochloric acid. At the time, he thought that the hydrogen gas was phlogiston – a substance which was mistakenly thought to have been released when burning a combustible body.

In 1774, Joseph Priestly conducted an experiment and released what he called a dephlogisticated gas. This experiment was also conducted by Antoine Lavoisier who first obtained calx of mercury, which at that time was referred to as the ash that is formed when a substance is burned in the air. Antoine Lavoisier was able to obtain calx of mercury by burning mercury in air at moderate temperatures. The most exciting and transformative part of his experiment is however the decomposition of the calx of mercury into their respective mercury and oxygen parts. This remarkable achievement, which was also specified by Joseph Priestly, changed the history of chemistry, and overall, the discourse of Earth Sciences forever. Equally transformative discoveries of gases include the identification of nitrogen by Henry Rutherford in 1772 and the identification of noble gases by William Ramsey (1894 – 1889).

Remarkable progress has been made in atmosphere science after the elements that make up the atmosphere are identified. Thanks to the giants who devoted themselves for this worthy cause, now advances in Earth Sciences are moving with a staggering pace. The future is being realized now.

Atmospheric pressure and temperature measurements that were initially made by climbing mountains just within the lower limits of the troposphere, are now being made through the entire column of the troposphere, the stratosphere, the Mesosphere, and the Thermosphere using hi-tech balloons, aircrafts, and satellites, measuring the physical and compositional variations of over a 1000 km thick vertical column of air.

However, there is still much to be done to understand the origin and the evolution of the atmosphere and its interactions with the biosphere, the geosphere, and the cryosphere. This might indeed appear as a daunting task. However, as the history of atmospheric science clearly shows, extremely consequential observations maybe made by beginning at the beginning and by asking the right questions.

© Authored by Luel Emishaw, Burst of Insights

The Atmosphere Paul I Palmer

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