Mineralogy Presentation

Mineralogy PresentationMinerals, origin, occurrence and associations Rock forming minerals Classification, Description and Uses1References.The following books are also useful compilations of mineral data and descrip tions. W.A. Deer, R.A. Howie and J. Zussman (1962, 1974, 1980) Rock Forming Minerals (Seven Volumes) Longmans, London. R.W.G. Wyckoff (1964) Crystal Structures. Wiley (New York) (Eight Volumes) (Vols 1, 2, 3 and 4 contain mineral structures). T. Zoltai and J. M. Stout (1985) Mineralogy: Concepts and Principles. Burgess (Minneapolis). C. Klein and C.S. Hurlbut, Jr. (1993) Manual of Mineralogy (After J.D. Dana, 21st edition). Wiley, (New YorkL.G. Berry, B. Mason, and R.V. Dietrich (1983) Mineralogy (Second Edition) Freeman (San Francisco). W.H. Balckburn and W.H. Dennen (1988) Principles of Mineralogy . W.C. Brown, K. Frye (1974) Modern Mineralogy. Prentice-Hall. Deer, Howie, Zussman (1992) An Introduction to the Rock Forming Minerals (Second Edition) London Longmans ISBN 0-582-30094-0. 696pp. 2Mineralogy It is the study of the chemistry, physics and crystal structure of natural, solid, crystalline materials known as mineral i.e. is the study of minerals. It also includes the study of origin, processes of mineral formation, their geographical distribution, classification, as well as utilization.

3Importance of MineralogyMinerals are the building blocks of the planet. The study of the earth materials depends on an understanding of minerals making up the rocks and sedimentsMineral resources: Ore minerals are the source of valuable metals (e.g. Cu, Au) and provide energy resources like uranium. Certain forms of minerals, gems, delight the eye as jewelry. Industrial / agro minerals serve as the raw materials for manufacturing chemicals, dimension stones, aggregates (metals) for road and concrete , etc.Soil formation processesUnfortunately, not all minerals are beneficial; some pose environmental hazards (geological hazards)

4DEFINITIONA mineral is a naturally occurring homogeneous solid with a definite chemical composition and ordered atomic arrangement formed usually by inorganic processes.

5Explanation of Definition1 Naturally OccurringMinerals are not synthetic (made in a laboratory)Synthetic equivalents of minerals have the qualifier synafter their names

6Explanation of Definition Cont.2 HomogenousMinerals cannot be broken down into smaller chemical partsA mineral is considered a single phasein a thermodynamic sense

7Explanation of Definition Cont.3 SolidMinerals are not gases or liquidsThe exception is liquid mercury (Hg)

8Explanation of Definition Cont.4 Definite chemical compositionMinerals are made up of elements which are present as atoms or ions or radicalsExamples: silicates: Si4++ O2- SiO44-carbonates: C4+ + O2- CO32-phosphates: P5+ + O2- PO43-Carbon: C9Explanation of Definition Cont.5 Highly-ordered atomic arrangementMinerals are formed by a regularly-arranged internal framework of atoms

10Explanation of Definition Cont.6 InorganicMinerals are not organic compounds (i.e. composed solely of C,H,N & O) and are not biological in origin

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MineraloidNatural materials which resemble minerals in all ways except for one of the 6 criteriae.g. volcanic glass amorphous (only short-range order)e.g. Metamict minerals: minerals which have lost their internal order (destroyed) due to self-inflicted radiation damage (radioactive decay of some elements) e.g. Uranium 12Mineral FormationThe origin of chemical elements:Many theories exist one of which is the Big Bang theory.Cosmic explosion produced among other particles, protons, neutrons, and electrons which rapidly became organized into the elements, e.g. hydrogen (1 proton, 1 electron).These primitive elements expanded, gravitational instabilities caused parts to coalesce into huge clouds.13Mineral Formation Cont.Cooling of gaseous elements precipitated first heavy elements in a form of solid particles dust.First precipitates were crystals (minerals) of platinum-group metals, followed by aluminium oxides, metallic nickel-iron, and Mg silicates then came more complex silicates and various sulphides of heavy metals. Hence the earth accreted from these early solid particles called chondrules.

Mineral Formation Cont.The influx of solid particles it got hot enough to melt so that the dense Ni-Fe metal together with elements soluble in the metal sank to the centre and formed the core.The lighter oxygen-bearing minerals (mostly silicates) formed the mantle. So the earth today is made up of solid minerals to a depth of about 2900 km.

Mineral Formation Cont.Formation Processes:1 Precipitation2 Sublimation3 Crystallization4 Solid - Solid reactions (Recrystallization)

Mineral Formation Cont.

Precipitation (settling or fall out) from a fluid like H2O. Within the Earth: by hydrothermal processes, diagenesis, and metamorphism,At or near the Earth's surface: by evaporation, weathering, or biological activity.Sublimation from a vapour. This process is somewhat rare, but can take place at a volcanic vent, or deep in space where the pressure is near vacuum.

17Mineral Formation Cont.

Crystallization from a liquid. This takes place during crystallization of molten rock (magma) either below or at the Earth's surface.Solid - Solid reactions. This process involves minerals reacting with other minerals in the solid state to produce one or more new minerals. Such processes take place during metamorphism and diagenesis due to changing temperature and pressure conditions.Environments

The environments of mineral formation geologically are highly varied; within the Earth's crust, different temperatures and depths result in varied minerals andon the Earths Surface, low temperature lead to precipitation from saline brine (slightly salty water). 19Environments Cont.

Based on energy sources environment is groups as: 1 Endogenetic (hypogene)- deep-seated processes in the interior of the earth.2 Exogenetic (hypergene)- surface processes (at or near the earths surface as well as in the atmosphere and hydrosphere).

Mode of OccurrenceMagmatic- crystallization from an igneous magma or lavaPegmatitic final stage crystallization of magmaPneumatolitic - sublimation from volcanic gasesHydrothermal deposition from hot water and steam 21Mode of Occurrence Cont.Metamorphic and Metasomatic recrystallization of existing mineralsEvaporites - sun evaporates water and leaves saltCrystallization during diagenesis of sediments Formation by oxidation and weatheringIn geologic environments where mineral formation is taking place, the kinds of minerals that form depend on various factors such as:(a) Temperature (b) Pressure (c) The chemical activity of the water present (d) The mobility and relative abundance of chemical element. The mineral formed is defined by two fundamental properties:crystal structure the geometric arrangement of the ions (atoms) composing the minerals.chemical composition- the proportions of different chemical elements contained. 23Igneous MineralsMinerals in igneous rocks must have high melting points and be able to co-exist with, or crystallize from, silicate melts at temperatures above 800 C. Igneous rocks can be generally classed according to their silica content with low-silica (