INTRO: ROCKS & MINERALS Flashcards
Name two types of isotopes
Radioactive and Stable (Non-Radio Active)
A stable configuration occurs when a valence shell contains…
Eight Electrons
There are three main types of chemical bonds:
Ionic, Covalent, Metallic
Ionic Bonds:
transfer electrons between atoms
Covalent Bonds:
share electrons between atoms
Metallic Bonds:
valence electrons move freely among atoms
Diamond consists…
entirely of carbon atoms united by covalent bonds in a tetrahedral
structure with a repeating pattern of 8 atoms
Crystal lattice:
The 3-D molecular structure of a mineral;
its configuration reflects relative sizes and
numbers of ions that make up the mineral
To form a stable compound, the ions must have:
1) their ionic charges be in balance, and
2) right size to allow them to fit together
Cation Substitution:
Cations of similar size and charges tend to substitute for one
another in the crystal lattice and can form compounds having the same crystal
structure but different chemical composition
Definition of a mineral:
In geology, a mineral is a naturally occurring, inorganic solid, with a crystalline structure
and definite chemical composition formed by geological processes
Characteristics of a Mineral:
- naturally occurring
- inorganic
- solid
- characteristic crystalline structure
- definite chemical composition
Crystalline solid
Minerals exhibit an ordered internal structure in which in which the atoms are
arranged in a regular, repeating pattern
Chemical composition of a mineral and the way in which atoms are bonded
determines:
- Mineral shape and appearance
- Mineral hardness
- The way in which a mineral breaks, also known as cleavage or fracture
- The specific gravity or weight of a mineral
- Optical properties such as color, luster, or diaphaneity
There are three types of diaphaneity:
*Transparent minerals transmit light freely
*Translucent minerals transmit light although it maybe hard to see through them
*Opaque minerals do not transmit light at all and appear solid
Three Main Types of Lustre:
- Metallic luster: appearance of polished metal
- Non-metallic luster: does not look like metal
- Sub-metallic luster: somewhat metallic without a polished sheen
Moh’s scale of hardness:
Relative scale of hardness
Softest (1) talc – hardest (10) diamond
Cleavage is described by:
- Number of planes
- Angles between adjacent planes
- Constant for a particular mineral
Fracture:
- Some minerals break unevenly (fracture) and do not exhibit cleavage
– Smooth, curved surfaces when minerals break in a glass-like manner:
conchoidal fracture
– Others include fibrous and rough fracture (asbestos)
Silicates
- Silicates are the most abundant group of minerals in the crust and mantle;
- They contain silicon bonded to an oxygen
in a unit structure known as the
silica tetrahedron;
– 4 oxygen atoms (-8) surround a much smaller silicon atom (+4)
- Most silicate minerals form at high temperatures
How tetrahedra may be linked:
- independent tetrahedra (olivine, garnet)
- single chains (pyroxene group)
- double chains (amphibole group)
- Sheets (mica group)
- Framework (feldspars and quartz)
Feldspar groups:
- Alkali feldspars
(potassium or K-spar)
* Orthoclase, sanidine, microcline, anorthoclase
- Plagioclase feldspars
(solid solutions between Na and Ca)
* Albite (Na) to Anorthite (Ca)
Non-Silicates:
– Carbonates
– Sulfates
– Sulfides
– Halides
– Oxides
– Native elements
Carbonate Minerals
Unlike silicates, most carbonates form at low temperatures near the Earth’s
surface – precipitated from solution in shallow seas or from groundwater
Prominent carbonate rocks include limestone and dolostone
Sulfate Minerals
Formed at low temperatures near the earth’s surface mainly through
evaporation of groundwater, lake, or ocean waters
Types of Sulfate Minerals:
Gypsum is a common sulfate mineral:
– Does not react with HCl
– Hardness of 2 (Moh’s Scale) easily scratched with fingernail
Alabaster:
fine-grained, massive gypsum
Plaster of Paris:
powdered form of calcium sulfate. When
water is added it forms a gypsum cement
Sulfide minerals are major ores of lead, zinc, copper, and molybdenum
Iron Oxides
Iron oxides form a small percentage of rocks
They are important ore bodies:
– magnetite (black streak and magnetic)
– hematite (rusty streak and not magnetic)
Halide Minerals
Halides have anions of the halogen elements (fluorine, chlorine, bromine, iodine).
– Halides are made of ionic bonds
– Form as mineral-rich waters evaporated
– Halite (sodium chloride - NaCl) is salt
– Sylvite (potassium chloride - KCl) is a potassium salt (potash)
Native Elements
- Minerals of a single element
– Gold, Silver, Copper, Sulphur
Rock:
Consolidated solid material comprised of aggregates of one or more
minerals or solidified organic material.
Most rocks consist of more than one mineral, for example granite = quartz,
feldspar, mica, and hornblende.
Some rocks are composed of only one mineral, for example limestone formed
from coral reefs (calcite).
Three
fundamental rock types that reflect their origin and processes of formation:
- Igneous,
- Sedimentary
- Metamorphic
Igneous rocks:
are derived from the cooling and crystallization of molten rock
Intrusive (Plutonic)
magma emplaced at depth
Extrusive (Volcanic)
lava extruded at surface
Sedimentary rocks:
are formed from the weathered remnants of pre-existing
rock (sediment) that has been compacted or cemented (i.e., process of
lithification)
or from minerals precipitated from water by chemical or biological
processes
Metamorphic rocks:
are formed by the transformation of pre-existing rock by:
- high temperature,
- high pressure, and
- chemically active fluids.
