Minerology

From SEG Wiki
Jump to: navigation, search

Mineralogy

Mineralogy is a subject of geology specializing in the scientific study of chemistry, crystal structure, and physical (including optical) properties of minerals and mineralized artifacts. Specific studies within mineralogy include the processes of mineral origin and formation, classification of minerals, their geographical distribution, as well as their utilization.

History of mineralogy

Early writing on mineralogy, especially on gemstones, comes from ancient Babylonia, the ancient Greco-Roman world, ancient and medieval China, and Sanskrit texts from ancient India and the ancient Islamic World. [1]. Books on the subject included the Naturalis Historia of Pliny the Elder, which not only described many different minerals but also explained many of their properties, and Kitab al Jawahir (Book of Precious Stones) by Persian scientist Al Biruni. The German Renaissance specialist Georgius Agricola wrote works such as De re metallica (On Metals, 1556) and De Natura Fossilium (On the Nature of Rocks, 1546) which began the scientific approach to the subject. Systematic scientific studies of minerals and rocks developed in post-Renaissance Europe. [1]. The modern study of mineralogy was founded on the principles of crystallography (the origins of geometric crystallography, itself, can be traced back to the mineralogy practiced in the eighteenth and nineteenth centuries) and to the microscopic study of rock sections with the invention of the microscope in the 17th century. [1]

Nicholas Steno first observed the law of constancy of interfacial angles (also known as the first law of crystallography) in quartz crystals in 1669. [2]rp|4. This was later generalized and established experimentally by Jean-Baptiste L. Romé de l'Islee in 1783. [3]. René Just Haüy, the "father of modern crystallography", showed that crystals are periodic and established that the orientations of crystal faces can be expressed in terms of rational numbers, as later encoded in the Miller indices. [2]rp|4 In 1814, Jöns Jacob Berzelius introduced a classification of minerals based on their chemistry rather than their crystal structure.[4] William Nicol (geologist)|William Nicol developed the Nicol prism, which polarizes light, in 1827–1828 while studying fossilized wood; Henry Clifton Sorby showed that thin sections of minerals could be identified by their optical properties using a polarizing microscope.[2]rp|4[4]rp|15 James D. Dana published his first edition of A System of Mineralogy in 1837, and in a later edition introduced a chemical classification that is still the standard.[2]rp|4[4]rp|15 X-ray diffraction was demonstrated by Max von Laue in 1912, and developed into a tool for analyzing the crystal structure of minerals by the father/son team of William Henry Bragg and William Lawrence Bragg.[2]rp|4

More recently, driven by advances in experimental technique (such as neutron diffraction) and available computational power, the latter of which has enabled extremely accurate atomic-scale simulations of the behaviour of crystals, the science has branched out to consider more general problems in the fields of inorganic chemistry and solid-state physics. It, however, retains a focus on the crystal structures commonly encountered in rock-forming minerals (such as the perovskites, clay minerals and Tectosilicate|framework silicates). In particular, the field has made great advances in the understanding of the relationship between the atomic-scale structure of minerals and their function; in nature, prominent examples would be accurate measurement and prediction of the elastic properties of minerals, which has led to new insight into seismology|seismological behaviour of rocks and depth-related discontinuities in seismograms of the Earth's mantle. To this end, in their focus on the connection between atomic-scale phenomena and macroscopic properties, the mineral sciences (as they are now commonly known) display perhaps more of an overlap with materials science than any other discipline.

Physical properties

An initial step in identifying a mineral is to examine its physical properties, many of which can be measured on a hand sample. These can be classified into density (often given as specific gravity); measures of mechanical cohesion (Mohs scale|hardness, Tenacity (mineralogy)|tenacity, Cleavage (crystal)|cleavage, Fracture (mineralogy)|fracture, Cleavage (crystal)#Parting|parting); macroscopic visual properties (Luster (mineralogy)|luster, color, Streak (mineralogy)|streak, luminescence, Transparency and translucency|diaphaneity); magnetic and electric properties; radioactivity and solubility in hydrogen chloride (Chemical formula|H||Cl|).[2]rp|97–113[5]rp|39–53

Mineral magnetite (lodestone), from Tortola, British Virgin Islands

An example of the mineral, which possesses strong magnetic properties is the mineral magnetite, lodestone, from Tortola, British Virgin Islands; found in igneous plutonic rocks[6] formations, composed of several minerals, including quartz, plagicase, alkali feldspar, biotite and titanite.[7]

If the mineral is well crystallized, it will also have a distinctive crystal habit (for example, hexagonal, columnar, botryoidal) that reflects the crystal structure or internal arrangement of atoms.[5]rp|40–41 It is also affected by crystal defects and Crystal twinning|twinning. Many crystals are polymorphism (materials science)|polymorphic, having more than one possible crystal structure depending on factors such as pressure and temperature.[2]rp|66–68[5]rp|126

Polymorphism in crystallography, the condition, when the mineral of a single solid chemical composition, can have more than one crystal structure, however the results of the research work of the scientists from the University of Bristol in 2016, proved that polymorphism can be controlled, what is opening a new way to grow crystals: Dr Hall said: “The application of magnetic fields to intentionally control polymorphism is entirely novel...”[8] Examples of polymorphs are calcite and aragonite - two minerals with identical chemical composition, distinguished by their crystallography: calcite is rhombohedral and aragonite is orthorhombic.

Crystal structure

perovskite crystal structure. The most abundant mineral in the Earth, bridgmanite, has this structure.[9] Its chemical formula is (Mg,Fe)SiO3; the red spheres are oxygen, the blue spheres silicon and the green spheres magnesium or iron.

The crystal structure is the arrangement of atoms in a crystal. It is represented by a Crystal lattice|lattice of points which repeats a basic pattern, called a unit cell, in three dimensions. The lattice can be characterized by its symmetries and by the dimensions of the unit cell. These dimensions are represented by three Miller index|Miller indices.[10]rp|91–92 The lattice remains unchanged by certain symmetry operations about any given point in the lattice: Reflection symmetry|reflection, Rotational symmetry|rotation, Point reflection|inversion, and Improper rotation|rotary inversion, a combination of rotation and reflection. Together, they make up a mathematical object called a crystallographic point group or crystal class. There are 32 possible crystal classes. In addition, there are operations that displace all the points: Translational symmetry|translation, screw axis, and glide plane. In combination with the point symmetries, they form 230 possible space groups.[10]rp|125–126

Most geology departments have X-ray powder diffraction equipment to analyze the crystal structures of minerals.[5]rp|54–55 X-rays have wavelengths that are the same order of magnitude as the distances between atoms. Diffraction, the constructive and destructive interference between waves scattered at different atoms, leads to distinctive patterns of high and low intensity that depend on the geometry of the crystal. In a sample that is ground to a powder, the X-rays sample a random distribution of all crystal orientations.[11] Powder diffraction can distinguish between minerals that may appear the same in a hand sample, for example quartz and its polymorphs tridymite and cristobalite.[5]rp|54

Isomorphism (crystallography)|isomorphous minerals of different compositions have similar powder diffraction patterns, the main difference being in spacing and intensity of lines. For example, the Chemical formula|Na||Cl (halite) crystal structure is space group Fm3m; this structure is shared by sylvite (Chemical formula|K||Cl), periclase (Chemical formula|Mg||O), bunsenite (Chemical formula|Ni||O), galena (Chemical formula|Pb||S), alabandite (Chemical formula|Mn||S), chlorargyrite (Chemical formula|Ag||Cl), and Titanium nitride|osbornite (Chemical formula|Ti||N).[12]rp|150–151

Chemical elements

A few minerals are chemical elements, including sulfur, copper, silver, and gold, but the vast majority are Chemical compound|compounds. Before about 1947, the main method for identifying composition was wet chemical analysis, which involved dissolving a mineral in an acid such as hydrochloric acid (Chemical formula|H||Cl|). The elements in solution were then identified using Colorimetry (chemical method)|colorimetry, Titration|volumetric analysis or gravimetric analysis.[12]rp|224–225 A variation on the wet methods is atomic absorption spectroscopy, which also requires the dissolution of the sample but is much faster and cheaper than the above methods. The solution is vaporized and its absorption spectrum is measured in the visible and ultraviolet range.[12]rp|225–226 Other techniques are X-ray fluorescence, electron microprobe analysis and Atomic emission spectroscopy|optical emission spectrography.[12]rp|227–232

Optical

In addition to macroscopic properties such as color or lustre, minerals have properties that require a polarizing microscope to observe.

Formation environments

The environments of mineral formation and growth are highly varied, ranging from slow crystallization at the high temperatures and pressures of igneous melts deep within the Earth's crust to the low temperature precipitation from a saline brine at the Earth's surface.

Various possible methods of formation include [13]

  • sublimation from volcanic gases
  • deposition from aqueous solutions and hydrothermal brines
  • crystallization from an igneous magma or lava
  • recrystallization due to metamorphic processes and metasomatism
  • crystallization during diagenesis of sediments
  • formation by oxidation and weathering of rocks exposed to the atmosphere or within the soil environment.

Uses

Minerals are essential to various needs within human society, such as minerals used as ores for essential components of metal products used in various commodities and machinery, essential components to building materials such as limestone, marble, granite, gravel, glass, plaster, cement, etc. [13] Minerals are also used in fertilizers to enrich the growth of agricultural crops.

Collecting

Mineral collecting is also a recreational study and collection hobby, with clubs and societies representing the field. [14][15]. Museums, such as the Smithsonian National Museum of Natural History Hall of Geology, Gems, and Minerals, the Natural History Museum of Los Angeles County, the Natural History Museum, London, and the private Mim Mineral Museum in Beirut, Lebanon, | url = | journal = The Mineralogical Record | volume = 45 | issue = 1| pages = 61–83 }}</ref>[16] have popular collections of mineral specimens on permanent display.[17]

Notes

  1. 1.0 1.1 1.2 Needham, Joseph (1959). Science and civilisation in China. Cambridge: Cambridge University Press. pp. 637–638. ISBN 978-0521058018.
  2. 2.0 2.1 2.2 2.3 2.4 2.5 2.6 Nesse, William D. (2012). Introduction to mineralogy (2nd ed.). New York: Oxford University Press. ISBN 978-0199827381.
  3. "Law of the constancy of interfacial angles". Online dictionary of crystallography. International Union of Crystallography. 24 August 2014. http://reference.iucr.org/dictionary/Law_of_the_constancy_of_interfacial_angles. Retrieved 22 September 2015.
  4. 4.0 4.1 4.2 Rafferty, John P. (2012). Geological sciences (1st ed.). New York: Britannica Educational Pub. in association with Rosen Educational Services. pp. 14–15. ISBN 9781615304950.
  5. 5.0 5.1 5.2 5.3 5.4 Klein, Cornelis; Philpotts, Anthony R. (2013). Earth materials : introduction to mineralogy and petrology. New York: Cambridge University Press. ISBN 9780521145213.
  6. "images". G.Hayes. http://geotripperimages.com/Earth_Materials/plutonic_igneous_rocks.html. Retrieved 21 October 2016.
  7. "petrography". google p.105. https://books.google.co.uk/books?id=WWWRi2zB9bsC&pg=PA105&lpg=. Retrieved 21 October 2016.
  8. "news". University of Bristol. http://www.bristol.ac.uk/news/2016/may/new-way-of-growing-crystals.html. Retrieved 21 October 2016.
  9. Sharp, T. (27 November 2014). "Bridgmanite--named at last". Science 346 (6213): 1057–1058. doi:10.1126/science.1261887. PMID 25430755.
  10. 10.0 10.1 Ashcroft, Neil W.; Mermin, N. David (1977). Solid state physics (27. repr. ed.). New York: Holt, Rinehart and Winston. ISBN 9780030839931.
  11. Dinnebier, Robert E.; Billinge, Simon J.L. (2008). "1. Principles of powder diffraction". Powder diffraction : theory and practice (Repr. ed.). Cambridge: Royal Society of Chemistry. pp. 1–19. ISBN 9780854042319.
  12. 12.0 12.1 12.2 12.3 Klein, Cornelis; Hurlbut, Jr., Cornelius S. (1993). Manual of mineralogy : (after James D. Dana) (21st ed.). New York: Wiley. ISBN 047157452X.
  13. 13.0 13.1 harvnb|Ramsdell|1963
  14. "Collector's Corner". The Mineralogical Society of America. http://www.minsocam.org/MSA/collectors_corner/index.htm. Retrieved 2010-05-22.
  15. "The American Federation of Mineral Societies". http://www.amfed.org/. Retrieved 2010-05-22.
  16. Opening of the MIM Museum, 12 Oct. 2013
  17. "Gems and Minerals". Natural History Museum of Los Angeles. http://www.nhm.org/site/explore-exhibits/permanent-exhibits/gems-minerals. Retrieved 2010-05-22.

References

  • Gribble, C.D.; Hall, A.J. (1993). Optical Mineralogy: Principles And Practice.. London: CRC Press. ISBN 9780203498705.
  • Tisljar, S.K. Haldar, Josip (2013). Introduction to mineralogy and petrology. Burlington: Elsevier Science. ISBN 9780124167100.
  • Moses, Alfred J. (1918–1920). "Mineralogy". In Ramsdell, Lewis S.. Encyclopedia Americana: International Edition. 19. New York: Americana Corporation. pp. 164–168.
  • Perkins, Dexter (2014). Mineralogy. Pearson Higher Ed. ISBN 9780321986573.
  • Rapp, George R. (2002). Archaeomineralogy. Berlin, Heidelberg: Springer Berlin Heidelberg. ISBN 9783662050057.