Chapter-3 Mineralogy Flashcards
are naturally occurring, solid earth materials formed by geologic processes.
Minerals
– is composed of atom, the smallest part of a chemical element that can take part in a chemical reaction or combine with another atom.
All matter- including rocks, minerals, water etc.
are atoms of the same (atomic number) with different neutrons in the nucleus (variable atomic mass number)
Isotopes
Isotopes that are unstable and undergo nuclear decay (spontaneously change and emit nuclear radiation) are called
Radioisotopes
A mineral is formally defined as an element or a chemical compound that must:
- Be naturally-formed. (Excludes human-made diamonds)
- Normally be a solid. (Excludes fluids)
- Have a characteristic chemical formula
- Have a characteristic crystalline structure
substance composed of two or more elements that can be represented by a chemical formula
Compounds
note:Minerals can either be elements or compounds
Mineral Indetification
Chemical Composition
Physical Characteristics
attraction between atoms, sharing of electrons or both
Chemical bond
sharing of electrons (diamond)
Covalent bond
attraction of negatively and positively charged ions, more soluble, dissolves usually in water (halite, Na+, Cl-)
Ionic bond
weak attraction between chains of ions that themselves are bonded by stronger covalent/ionic bonds (graphite)
Van der Waals bond
– attraction between metal atoms (gold)
Metallic bond
Minerals that include the elements silicon Si and oxygen O in their chemical composition
Most abundant of the rock-forming minerals
Silicates
Form of silicon dioxide SiO2, one of the most abundant silicates in the crust of the earth
Fractures conchoidally (similar to shells)
Colorless/clear, some may contain impurities
Harder than glass
Quartz
are aluminosilicates, containing Si, O, Al, in combination with K, Na or Ca in a network of Si-O tetrahedra
Constituting 60% of the crust
Commercially important in the ceramics and glass industries
Feldspars
2 major types of Feldspars
Alkali feldspar (contains K) and Plagioclase feldspar (contains Na or Ca)
-minerals are group of silicates where Si and O combine with Fe and Mg.
Not very resistant to weathering, they tend to be altered or removed from their location relatively quickly.
Ferromanganesian Minerals
Three groups of Fe-Mg minerals:
Olivine – formed from magma solidification
Pyroxene – formed from pure Fe-Mg substituting for each other
Amphibole – double-chained Si-O tetrahedra
are minerals that contain the oxide anion O2- bonded to one or more metal ions.
Oxides
Types of oxides:
Hematite – contains iron Fe2O3
Bauxite – mixture of several aluminum oxides
Magnetite – contains iron Fe3O4 and a natural magnet
Contains the carbonate ion CO3,2-
Major constituent of limestone and marbles.
Carbonates
are minerals with a dominant halide (halogens, Group 17) anions F-, Cl-, Br-, I-
Halides
Most common halide is ?
Table Salt (NaCl) also known as halite
Minerals containing sulfur anion S2-
Always associated with environmental degradation.
Sulfides
Minerals containing the sulfate ion (SO4,2-) within their structures
Sulfates
Minerals containing phosphate anion (PO4,3-) along with vanadate, arsenate, chorine, fluorine and hydroxide anions
Phosphates
Minerals formed of a single element, such as gold, silver, copper, diamond (carbon)
They have long been sought as valuable minerals
Native Element Minerals
Physical Characteristics of a minerals are identified through?
Color Streak Luster Density Hardness Cleavage Fracture
is the perception when different wavelengths of visible light are incident upon the eye.
Color
are minerals that exhibit coloration that is directly related to its chemical composition
Idiochromatic Minerals
are minerals that exhibit coloration due to presence of an impurity, foreign element or a defect in its lattice structure
Allochromatic Minerals
is the color of a mineral substance when it has been ground to a fine powder
Streak
refers to the way light is reflected from the mineral.
Luster
Two types of Luster:
Opaque has high rate of light absorption (20-50% reflection of incident light)
Transparent permits passing of lights into it (5-20% reflection of incident light)
Two categories of mineral luster:
Metallic and Nonmetallic
reflect light very poorly and do not shine.
Dull/earthy Luster
possesses a sheen resembling that of resin, with refractive index greater than 2.0
Reisnous Luster
appears iridescent, opalescent or pearly
Pearly Luster
appears to be covered with a thin layer of oil
Greasy Luster
occurs when light is reflected off of an aggregate of fine parallel fibers
Silky Luster
occurs in minerals with predominant ionic bonding and resembles the reflective quality of a broken glass
Vitreous Luster
are highly dispersive and translucent, has a sparkling reflection of diamond
Adamantine or Brilliant Luster
is the level of difficulty with which a smooth surface of a mineral specimen may be scratched.
Hardness
is the tendency of minerals to split along a definite structural planes, usually in planes where there are weaker bond strengths
Cleavage
Quality of a cleavage:
Eminent Perfect Distinct Difficult Imperfect Indistinct
cleavage occurs readily; difficult to prevent from occurring
Eminent
– cleavage breaks easily, exposing continuous, flat surfaces which reflect light
Perfect
implies that cleavage surfaces are present, although they are marred by fractures or imperfections
Distinct
occurs when a mineral is split in a direction which does not serve as a plane of perfect or distinct cleavage
Fracture
Types of fractures:
Conchoidal
Irregular/uneven
Hackly
results in a series of smoothly curved concentric rings about a stressed point, producing a shell-like appearance
Conchoidal Fracture
fracture results in a rough, rugged surface
Irregular/Uneven Fracture
describes a fractured surface with multiple small, sharp and jagged irregularities.
Hackly Fracture
