Likewise, there are a small number of naturally formed compounds that are amorphous , meaning that they are never found in a crystalline state: the copper carbonate georgeite is an example of an amorphous compound that is officially regarded as a mineral. These few exceptions apart, we have a very straightforward definition to work with.
In the same paper, the author goes on to make the distinction that compounds that have formed on materials of anthropogenic origin, such as metal-rich smelter-slags, are not to be regarded as minerals.
Compounds that have formed on substrates of natural origin that have been exposed to geological processes by anthropogenic activities — such as tunneling or making road-cuttings, which could result in rocks being exposed to weathering agents — can be regarded as minerals. At the time that this definition was published, there was a degree of dissent within the mineral collecting community, because the compounds occurring as a result of weathering of ancient smelter-slags often form beautiful, colourful crystals lining cavities in the slags.
One suspects that this aspect of the definition of a mineral, and to what extent human activity should be included or excluded from Nature, will continue to prompt lively debate for years to come!
And what about the crystalline compounds and elements of extraterrestrial origin? This seems reasonable enough. Terms often have to be adapted as circumstances change through the progress of science. So let us now further dissect the definition, firstly looking at what a chemical compound is and how it forms, and secondly, looking at crystals and crystal formation. We will look at the geological processes that lead to the formation of mineral deposits in later chapters; here we deal with the basics.
Both elements and chemical compounds consist of the basic units of matter: atoms. An element , in its pure form, consists entirely of atoms of itself: thus pure gold consists entirely of atoms of gold. In nature, such purity is virtually unheard-of, so that the native elements will consist almost entirely of atoms of themselves, but will also include impurities — atoms of other elements. Compounds consist of atoms of two or more elements combined and held together by chemical bonds.
So how does that work? To find out, we need to start with the basics: what are atoms, and how they may bond to one another to make cohesive substances?
The nucleus consists of one or more protons , which carry a positive charge, and neutrons which, as the name suggests, are neutral, and with a similar mass to protons. The electromagnetic force between the positively charged protons and the negatively charged electrons opposite charges strongly attract one another is what binds the whole thing together. Each chemical element has an atomic number which is defined by the number of protons in the nuclei of its constituent atoms.
Thus hydrogen — element 1 — has a single proton in its nucleus; copper — element 29 — has 29 protons, and lead — element 82 — has 82 protons, and so on. The number of neutrons plus the number of protons gives a second value — the mass number. Because the number of neutrons can vary a little, some elements occur in nature as several varieties with different mass numbers.
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These varieties are known as isotopes. An example is carbon: it has three isotopes — carbon 12, 13 and An atom of carbon 12 has six protons and six neutrons in its nucleus.
It is by far the dominant isotope, comprising Carbon 13, with six protons and seven neutrons, is stable but rare, making up 1. Carbon 14, also known as radiocarbon, is an unstable, radioactive isotope with six protons and eight neutrons, making up the extremely small remainder.
The electrons that surround the nucleus of an atom exist within a series of orbitals or shells , each being a zone of stable energy levels. Working outwards from the nucleus of an atom, the shells are labelled 1—6 and each holds a specific maximum number of electrons. Shell 1 can hold two electrons, shell 2 can accommodate eight; shell 3 eighteen, shell 4 thirty-two, and so on. For example, hydrogen, consisting of one proton and one electron, only has shell 1. Fluorine, with nine protons and nine electrons, has shells 1 and 2 — so there are two electrons in shell 1 and seven out of a possible eight in shell 2.
Neon has ten protons and ten electrons, so that shells 1 2 electrons and 2 8 electrons are both filled. Sodium, on the other hand, has 11 protons and 11 electrons, with shells 1 and 2 filled with two and eight electrons respectively, but with a single electron in the succeeding shell 3. The table below shows the electron configuration of elements 1—20, demonstrating how successive shells fill up with increased atomic number:. Electrons may move up or down from one shell to another, but to do this they must either absorb or emit energy: those closest to the nucleus are held, because of their proximity, by the strongest electromagnetic force, so cannot easily be moved outwards.
But for those electrons in the outermost shell, things are in most cases somewhat easier. Bailey , Hamilton College Author Profile.
The five categories included in the peer review process are. This teaching activity was originally published in: Brady, J.
All teaching activities in this volume received two external peer reviews from mineralogy faculty focused on content and pedagogy, and a final review by the co-editors to comply with the publication standards of the Mineralogical Society of America. Minerals are inorganic chemical compounds with a wide range of physical and chemical properties. Geologists frequently measure and observe properties such as hardness, specific gravity, color, etc.
Unfortunately, students usually view these properties simply as tools for identifying unknown mineral specimens.
One of the objectives of this exercise is to make students aware of the fact that minerals have many additional properties that can be measured, and that all of the physical and chemical properties of minerals have important applications beyond that of simple mineral identification. Please do not let the title of this exercise scare you away.
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Robert B. This structure is represented by a lattice of points which repeats basic pattern, known as the unit cell. Page 1 of 1. Otherwise, we have more than , ebooks to choose from. Mineralogy, I mused to myself, certainly has its moments. People have been fascinated by minerals since prehistory.
Mentioned in? References in classic literature? I am no specialist in mineralogy , and I went on down a very ruinous aisle running parallel to the first hall I had entered. View in context.
Morcerf had expected he should be the guide; on the contrary, it was he who, under the count's guidance, followed a course of archaeology, mineralogy , and natural history. She had taken her degree in geology and mineralogy in the University of London, and while working upon the auriferous rocks of North Wales, after a brief holiday spent in agitating for women's suffrage, she had been struck by the possibility of these reefs cropping up again under the water.
Their topics include lithium ion-conducting oxide garnets, crystallographic symmetry analysis in nickel-titanium shape memory alloys, applied mineralogy for recovery from the accident of Fukushima Daliichi Nuclear Power Station, patterns of mineral organization in carbonate biological hard materials, sea urchin spines as role models for biological design and integrative structures, and a procedure to apply spectroscopic techniques in the investigation of silica-bearing industrial materials.