ROCK - an aggregate of minerals. Examples
MINERAL - a naturally occurring inorganic solid that possesses a definite chemical structure, which gives it a unique set of physical properties. Again,
(glass, coal, oil, examples of what is not a mineral)
*the earth has about 4000 minerals, but only about a dozen are common rock forming minerals in the earth's crust.
The COMPOSITION and STRUCTURE of a MINERAL is based on the ELEMENTAL PROPERTIES and ARRANGEMENT of ATOMS within a DEFINITE PATTERN or FRAMEWORK.
The atomic number (that is the number of PROTONS in the nucleus) and the arrangement of electrons in shells surrounding the nucleus give the atom its electrical charge and atomic size characteristics.
Elements combine in definite proportions to form COMPOUNDS. (MINERALS are COMPOUNDS!) Based on electronic properties of atom, atoms form different kinds of bonds.
ISOTOPES - The MASS NUMBER of an ATOM is total of NEUTRONS and PROTONS. Some ELEMENTS have more than one mass based on variationss in the number of NEUTRONS.
The ATOMIC WEIGHT of an element is based on the average weight of
elements in their relative natural abundances. e.g. C12 and C14
RADIOACTIVITY is based on the instability of some ISOTOPES. Some isotopes break down to form lighter isotopes or different elements. This is important to the study of radiometric dating. For example, carbon has three isotopes: C12, C13, and C14. C14 is radioactive: it forms from incoming cosmic radiation striking nitrogen (N14) in the atmosphere ( neutron + N14 = C14 + proton ). C14 is then absorbed by living tissue. No new C14 is absorbed once an organism dies. C14 constantly slowly breaks down through time: ( C14 = N14 + beta- particle). Thus the amount of C14 in dead animals and plants decreases over time and the older the animal or plant fossil the less C14 is present.
CRYSTAL FORM is the external expression of the orderly internal arrangement of atoms. If a mineral can grow unrestricted, it will develop individual crystals with well formed crystal faces.
Other important properties of minerals are: LUSTER, COLOR, STREAK, HARDNESS, CLEAVAGE, FRACTURE, SPECIFIC GRAVITY. Other properties include fluorescence, phosphorescence, solubility, magnetic, radioactivity, piezoelectric, and "magical power " according to some folks....
A comparison of quartz and calcite:
SILICATES: (silicon-oxygen TETRAHEDRON, tetrahedrons form chains, double chains, and sheets.) See page 33
Common silicates are subdivided into groups:
BOWEN'S REACTION SERIES (p. 49, Chapter 3) - explains how the CRYSTALLIZATION process as magma cools, causes HIGH temperature minerals to form FIRST (mostly MAFIC minerals), and the LOW temperature minerals to form LAST (mostly FELSIC minerals). This causes the composition of the magma to change through time from mafic to more felsic. In a "magma chamber," a large volume of molten rock underground, this process is called MAGMATIC DIFFERENTIATION.
NATIVE (PURE) ELEMENTS (Composed of a single element) - gold, silver, carbon (diamond, graphite, coal), copper, platinum, and sulfur