After a long break, we are back with our articles. Today’s article will focus on minerals, which are the building blocks of rocks, that can greatly be used to go back in time and find the roots of life.
On Earth, more than 2000 varieties of minerals have been discovered. These substances are regarded as minerals according to the five criteria that the geologists use:
- The substance must be found as a solid in its natural form under the normal environmental conditions on Earth.
- The substance must be naturally found on Earth, not manufactured artificially.
- The substance must be inorganic; it should not be living or it should not be producible by living things.
- The substance must be made of specific elements that combine together in a fixed chemical formula.
- The substance must be made up of atoms that are arranged in an orderly manner.
As they are discovered, it has also been found that they can actually be used in a variety of applications in our daily lives. One of the most common examples of minerals in our everyday lives is fluorite, the mineral that is used to manufacture toothpaste.
The naming of the minerals has always been so random. No specific rule or criteria has been decided to name a newly discovered mineral, but instead, any characteristic feature of the mineral has been used. This ranges from the color of the mineral to its elemental composition and from the person who discovered it to the place it has been discovered. For example, the mineral albite gets its name from the Latin word albus which means ‘white’. Or, the mineral franklinite was named so because it has been majorly found in Franklin, New Jersey, United States. Although this causes some confusion sometimes among the scientific community, the International Mineralogical Association has been in an effort to control and standardize the naming of the minerals since 1960, the year which it started the Commission on New Minerals and Mineral Names to review the proposals for the names of the newly discovered minerals.
Before moving on to the categorization of the elements, it would be helpful to learn how the chemical compositions of the minerals are revealed as they would be used in some instances to classify the minerals into groups. For all chemically formed substances on Earth, it is the chemical composition and geometry that determines the physical and chemical properties of that particular substance. As for the minerals, various analytical techniques have been developed and utilized to determine which chemical elements and in which geometrical arrangements have the mineral been formed. One of the most common ways to determine the chemical composition of the minerals is through wet analytical methods. These methods, two of which are dissolution in acid and flame tests, include the dissolution of the mineral samples which are then precipitated and weighted. Another method is to use relatively newly developed instrumental techniques such as atomic absorption spectroscopy or X-ray diffraction. However, these techniques require expensive equipment and meticulous sample preparation procedures, and hence are not commonly preferred. But they are highly effective in determining any impurities that might be present in the sample, and thus, give more accurate results.
Some minerals, with the same chemical composition, may be found in two different naturally occurring forms on Earth. These are called the polymorphic forms of a mineral and mainly occur due to the changing behavior of the elements making up the mineral according to the changing environmental conditions such as temperature and pressure. The most common polymorphs on Earth are those made up of Carbon atoms: graphite is found in a hexagonal structure while diamond has an isometric structure.
The categorization and classification of minerals have always been a complex issue for geologists as minerals are so varied in terms of their colors, shapes, sizes, and textures. The most common classification of minerals is mainly according to the major anion that they contain. An anion is a negatively charged ion of an element that is formed when an element in its natural state gain electrons to complete its outer energy level and become energetically stable. Anions are one of the major contributors to the atomic arrangement of many minerals and thus, have been used to categorize the minerals. The most commonly known classes of minerals classified according to the anions they possess are oxides, silicates, and nitrates.
Another common way of classifying minerals is to classify them according to their crystal systems. Crystal systems have been created by grouping the symmetry elements — which are elements that determine the external shape of the mineral crystals. This external morphology can most of the time be determined by the human eye, unlike the internal morphology which can only be revealed by a combination of X-ray, neutron, and electron diffraction techniques, and thus gives a more understandable approach to the classification of minerals. This system of classification decreased the number of classifications as low as six: isometric, hexagonal, tetragonal, orthorhombic, monoclinic, and triclinic.
However recently, it has been found that every mineral has originated from different sources. This is an important discovery because if a proper classification according to this logic can be made, then the past times of the Earth can be found. In fact, it already started to be found. The researcher Robert Hazen and his colleagues have found that even the same minerals with the same chemical composition can come from different origins. It has already been known that minerals could form in all kinds of geological environments. The most common ones were magmatic conditions in which minerals form from the melted rocks; sedimentary conditions where the minerals were mostly formed from natural disasters such as erosion that created enough pressure for the formation of minerals; or hydrothermal conditions where the minerals precipitated from the hot solutions on the surface of the Earth. However, this new type of classification also includes the origins such as meteorites and stars, and thus, gives a better understanding of how the Earth could have been formed.
This discovery is now being discussed within the scientific communities as the research team has found that the environmental conditions that are suitable for life to be sustained have been around way before we were expecting them to – as early as 4.3 billion years ago. Along with their finding that nearly 80% of the mineral require water to be formed, this is an important finding as it may mean that those other planets which are now solid rocks may be available and suitable for life as long as water can be found. Who knows maybe Mars could really be our new home in the future!
 Stahl, Asa. “Earth’s Rock Collection Hints at How to Search for Life Elsewhere.” Science News Explores, 4 Aug. 2022, https://www.snexplores.org/article/earth-mineral-kingdom-classification-crystal-search-life.
 Sammartano, Mike. A Brief Introduction to Minerals. YouTube, 11 Jan. 2013, https://www.youtube.com/watch?v=8a7p1NFn64s. Accessed 9 Aug. 2022.
 Klein, Cornelis. “Mineral.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., https://www.britannica.com/science/mineral-chemical-compound/Compositional-variation.