What is mineralogy and why are we interested in minerals ?
Mineralogy is the science of minerals, their identification, characterisation and description, classification and origin. It studies minerals as associated constituents in rocks.
This discipline is closely linked to others, such as geology, petrology, planetology and physics-chemistry, and is also the subject of a great deal of industrial research. At the crossroads of different fields of activity, it is essential to understand and understand the mineral world.
The Roullier Endowment Fund’s Minerallium takes visitors on an interactive, educational guided tour to discover the role of minerals in the functioning of life on Earth, in animals and plants, from the Big Bang… to our plates!
What are minerals and how can they be identified? What are the main applications of mineralogy in our environment? How did mineralogy come about and what are the major milestones in its history? Finally, what are the main collections of minerals in museums and galleries? Dive into the world of minerals to find out!
Mineralogy, a multidisciplinary science with many applications
Over time, mineralogy and its corollaries – physics, chemistry and geology – have come to occupy an increasingly important place in our daily lives. Since 2015, humanity has extracted at least 70 billion tonnes of minerals every year, mainly from deep underground or open-air mines.
Mineralogy has become a multi-disciplinary science and is involved in a number of topical issues, from the origin of planets to high-tech materials, the protection of nature and biodiversity, the preservation of cultural heritage and human health.
Minerals and industry
Minerals are present in sometimes unsuspected ways, both in everyday objects and in the cutting-edge technologies that are shaping tomorrow’s uses. A car, for example, contains up to 150kg of minerals in tyres and plastic components, while paper and paints contain up to 50%. The physical and chemical properties sought are hardness, colour, purity, chemical inertness and thermal and electrical conductivity. Carbonates, silicas, talcs and clays are the main minerals extracted for industry in mines.
However, we must not overlook the group of metallic minerals, which constitute an important economic sector. The best known and most famous is gold, which is used not only in jewellery but also in certain electronic devices, because it is an excellent conductor of electricity and heat. The use of copper is also booming, thanks to its physical properties as an electrical conductor and its chemical properties as a bactericidal material in many medical products.
Health and minerals
The earliest healthcare practices, as far back as we can remember, made use of the resources of the surrounding natural environment, whether plants or… minerals. Clays have been used therapeutically since prehistoric times. In ancient times, iron salts were used as plasters to stop haemorrhaging, as were lead, sulphur, antimony and arsenic salts. From the sixteenth century onwards, practitioners began to make more and more regular use of mineral substances that were discovered to be essential to life.
The growth of industry since the nineteenth century, accompanied by the development of modern chemistry, has made the processes involved in creating medicines more sophisticated.
In this context, minerals have become raw materials from which chemical elements are extracted. Today, minerals have not disappeared from our bathrooms and first-aid kits! Around thirty mineral species continue to be used by the pharmaceutical and cosmetics industry for their remarkable physical and chemical properties (chemical compounds or properties such as hardness, colour, etc.). In our medicines, they are used to treat gastric reflux, diarrhoea and ulcers. They can be applied to the skin as antiseptics, dermatological protectors and sunscreens. Gypsum, a calcium sulphate, has been used since ancient times to make plaster!
In addition to the chemical properties of minerals, other even more surprising properties have been used since the beginning of the twentieth century: certain ores containing radioactive elements are the basis of a recent sector of medicine, nuclear medicine, with radiotherapy, for example, which consists of injecting a radioactive element into the body, which attaches itself to the diseased cells and destroys them.
Mineral identification and properties
Identifying a mineral is much more complex than recognising a mushroom or a bird! It’s a challenging task, even for many geology specialists, and mistakes are common, even if technology is helping us more and more these days.
Identifying samples that are sometimes very different requires a great deal of experience based on patient collecting, observation, cross-checking, discussion, visits to museums and galleries, reading and memorising. It also involves studying and quantifying the physical and chemical properties of the sample and the geological context in which it was found.
Physical properties and crystallography
The first step is to study the physical properties of a mineral. These are :
Colour, which depends on the light absorbed by the mineral.
Transparency. Some minerals are perfectly transparent (like rock crystal, for example), while others are translucent or opaque.
Radiance. Some minerals reflect light almost completely, like mirrors (e.g. gold, sulphides, pyrite). Others, such as clays, are dull. However, the most common lustre in the mineral world is vitreous, such as quartz.
Hardness. This is measured on a scale known as the Mohs scale, with 10 grades, from the softest (talc) to the hardest (diamond).
The second stage consists of studying the morphology of the mineral. This includes its external appearance (earthy, nodular, lamellar, fibrous) and the study of its crystals, known as crystallography. We then take into account, among other things :
- Its habitus (or appearance). This is the way in which the crystals combine within the mineral. These may be well-formed, isolated individual crystals, or more complex, disordered structures (lamellar, lenticular, fibrous, granular, etc.).
- Its crystalline structure, i.e. the geometric shapes of the crystals, made up of faces, edges and vertices. Crystals are classified into seven main crystal systems.
A wide variety of minerals
To date, according to current definitions, there are just over 4,750 different mineral species. Several dozen new species are discovered every year. Most often, these are microscopic species confined to a very specific deposit, having undergone unique geological episodes that explain their rarity. But the greatest potential for discovering new mineral species lies in the study of meteorites, which bear witness to unknown mineralogies on the Earth’s surface.
Another mineralogical world that is just beginning to be explored is that of minerals that are nanometric in size or that have little or no crystallisation. These species are impossible to detect using traditional mineralogical instruments. Their identification requires sophisticated instruments, such as synchrotron radiation accelerators, which have only recently been developed. The mineralogy of the future is on the march!
Great names and great moments in the history of mineralogy
From ancient beginnings…
Mineralogy is not a dead science: in fact, the definition of a mineral has constantly evolved over the ages. Prehistoric man already knew how to use different minerals and put them together. In Mesopotamia, around 3,500 BC, copper, zinc, gold and silver as well as numerous precious stones (malachite, turquoise, lapis lazuli, opal, agate) were used for ornaments, weapons and utensils. In fact, the various prehistoric periods are sometimes named in relation to man’s ability to use the minerals in his environment: Stone Age, Bronze Age, Iron Age, etc.
The Greek philosopher Aristotle was the first to write a scientific publication on minerals. His mineralogical system remained valid until the 16th century! In fact, during the Middle Ages in Europe, knowledge of minerals evolved very little. The books on the subject published at the time, the Lapidaries, were often summaries of ancient conceptions.
…For a topical subject!
The Renaissance saw a revival of the natural sciences. A Saxon-born physician, Georges Agricola (1494 – 1555), wrote the first scientific account of mines and minerals. He resolutely turned away from the alchemical approach in vogue in the Middle Ages and put forward his personal observations. He developed a systematic classification of minerals that would remain valid until the early 19th century. Agricola’s work was responsible for such a significant expansion of this science that he is considered to be the father of modern mineralogy.
The start of the industrial revolution in the 18th century gave a new impetus to the natural sciences. The increased demand for mineral raw materials required a scientific basis for the development of mineral extraction and the development of new deposits. Abbé René Just Haüy, a French mineralogist (1743 – 1822) proposed new nomenclatures and definitions: this was the birth of the crystalline systems. These criteria are still used today.
In France, mineralogy came to the fore and was popularised mainly as a result of the work carried out at the Muséum National d’Histoire Naturelle de Paris (MNHN), which was founded in 1793 and inherited the collections of the Jardin des Plantes. It brought together a large number of pre-existing mineralogical collections and set about developing and exhibiting them in the museum’s Galerie de Minéralogie.
Conclusion
As this article has shown, mineralogy is a multi-faceted science with a vast range of applications. Industry, health, materials chemistry, construction and even agriculture at the Minerallium… minerals are all around us in great numbers, and their variety is an asset in responding to a wide range of issues, from everyday problems to cutting-edge research.