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2009-06-02 12:31:41
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Mineralogy



Teacher: none for the moment


'Minerals are the basic stuff of the Earth, and their study will always remain at the core of the Earth Sciences' Frank C. Hawthorne, 1993



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Definition of a Mineral


A mineral is a naurally occuring solid with a highly ordered atomic arrangement and definite (but not fixed) chemical composition. It is usually formed by inorganic processes.

(Klein, C., 2002, The 22nd Edition Of The Manual Of Mineral Science (after James D. Dana), 641 pp )


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Physical Properties of Minerals in Hand Specimen


The physical properties of a mineral are an expression of the interrelation of a mineral’s structure and its chemical composition. In mineralogy courses the student is required to enroll in one or more related laboratory sessions. Usually the laboratory instruction starts with the study of minerals in hand specimen. For this study the use of the eyes and other unaided senses as well as some very basic testing tools leads to a very reasonably correct (or even unique) identification.

The properties that depend solely on visually inspection will be discussed first. These include the following:

Crystal form and habit
Intergrowths, twins and striations
State of aggregation
Luster, color, and streak
Other properties depending on light
Cleavage

This is followed by the evaluation of properties that require some relatively simple testing equipment:

Hardness
Specific gravity (or “heft”)
Magnetism
Radioactivity
Solubility in HCl


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Crystal Form and Crystal Habit


Commonly used terms to express the quality of the development of the external faces on a crystal:

Euhedral: From the Greek roots eu, meaning good, and hedron, meaning plane; describing a mineral that is completely bounded by crystal faces and hose growth during crystallization was not restrained or interfered with by adjacent crystals or mineral grains.

Subhedral : From the Latin root sub, meaning less than; dscribing a crystal or mineral grain that is partly bounded by crystal faces and partly by surfaces formed against preexisting grains.

Anhedral : Form the Greek root an, meaning without; for minerals that lack crystal faces and that may show rounded o irregular surfaces porduced by the crowding of adjacent minerals during crystallization.


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Here are some links related to the subject:

http://www.geolab.unc.edu/Petunia/IgMetAtlas/minerals/minerals.html

http://www.gly.bris.ac.uk/www/teach/opmin/mins.html 
( in this one you'll be abble to see minerals under the microscope )


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Back to Geology or the Elftown Academy


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Past teachers: [Vëaneron]

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