Download Elements and Minerals

Elements and Minerals
Chapter 1
Mineralogy, Dexter Perkins
Version: September 5, 2003
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mineralogy: study of minerals; petrology: study of rocks
This class will focus on hand specimen identification.
Studying for this class
o work together (try things alone first)
o recopy notes
o learn to spell correctly
o keep up
grades: cumulative point; percent on individual assignments is not as important as cumulative notes; some
tests will be very difficult with lower percentages; periodic quizzes in class
Have examples of physical properties for class on Friday (5th)
Knowing minerals
o name
o chemical composition, especially categories such as silicates, oxides, etc., and important cations
o origin of mineral (genesis); environment of formation
o crystal system & form
o uses
Knowing rocks
o name
o origin (genesis)
o common minerals
o textures
Introduction to Mineralogy
 People study minerals for different reasons.
 shirt: “If it can’t be grown it must be mined.” (There are a lot of synthetic polymers made in chemical
laboratories.)
 ~3000 minerals have been recognized. This call will study 30-40 silicate minerals and 30-40 non-silicate
minerals
 Minerals
o naturally occurring: excludes man-made substances, even though we can now grow many minerals
synthetically
o inorganic: no created by living organisms; CaCO3 (which is the same formula as a mineral) can be
formed by living organisms
o homogeneous solid: most minerals are solids
o definite chemical composition: the chemical formula is fixed within limits; some minerals have
wider limits than others
o definite crystalline structure:
 solids that have no crystal form, but fit all of the other requirements of minerals are called
mineraloids
 Minerals are sensitive to conditions (such as temperature and pressure), and so specific minerals only form
under a certain set of conditions. So some specific minerals are likely to form in close proximity to other
specific minerals, and some minerals do not form in close proximity to other specific minerals (mutually
exclusive).
 Mineral identification
o physical properties: optical properties (using thin sections), color. (X-ray diffraction, X-ray
fluorescence, and atomic absorption were listed as chemical properties, but I could consider them to
be physical properties, since samples maintain their chemical composition—there is no destruction
of the sample). We will use mostly simple physical properties in this class. Simple physical
observation is less specific, and therefore more prone to error.
o chemical properties: reaction with acids, dissolution, precipitation
o hardness and cleavage are determined by crystal structure and chemical composition
Classification of Minerals
 Can categorize by prominent cation; good for economics, but not good for the genesis of the mineral.
 Categorize by anion gives fewer groups.
 Main groups: silicates (this groups is large and is divided into subgroups), halides, sulfates, sulfides, oxides,
carbonates, hydroxides (see Table 2.5 in text). This class will use Appendix A classification system.
Chemistry
 bonding: ionic, covalent, metallic
 Type of bonding in mineral effects physical (and chemical) properties. (Table 1.3, also Figure 1.11,
Figure 1.12)
 Text, p. 19
o siderophile (element concentrated in iron-rich liquid)
o chalcophile (element concentrated in sulfur-rich liquid)
o lithophile (element concentrated in silica-rich liquid)
o atomophile (element forms a gas)
 Text, p. 23: mineral elements
o major elements: fundamental, determine mineral structure & properties
o minor elements: replacements of major elements
o trace elements: concentration not high enough to effect properties except maybe color