Chapter 2 Flashcards
(20 cards)
Define minerals
A mineral is a naturally occurring, inorganic crystalline solid that has a definite chemical composition, and an ordered internal (atomic) structure.
What are minerals made up of?
they are made up of atoms or ions of chemical elements.
(i) Atoms of gold or silver form native gold or silver minerals, C-atoms form diamond.
(ii) but most minerals are made-up of ions (both cations and anions)
List the most abundant elements in Earth’s crust along with their percentage.
Oxygen (O) => 46.3% Silicon (Si) => 28.2% Aluminum (Al) => 8.2% Iron (Fe) => 5.6% Calcium (Ca) => 4.1%
List the most abundant elements in the whole Earth.
Iron (Fe) => 34.6% Oxygen (O) => 29.5% Silicon (Si) => 15.2% Magnesium (Mg) => 12.7% Nickel (Ni) => 2.4% All other elements => 2.7%
What is the most abundant element in the universe?
Hydrogen (only one proton)
What are ions?
Are electrically charged atoms that have either lost or gained electrons.
- Cations are positively charged ions (loss of electron) ex. Ca2+, Si4+, etc.
- Anions are negatively charged ions (gain of electron) ex. O2-, Cl-
How do minerals form?
- Crystallization from magma: minerals form by cooling a mass of hot molten rock material (magma or lava), where the size of crystals depends upon temperature, pressure, and rate of cooling (slow vs. fast cooling)
- Crystallization from liquid: crystal growth in the solid state, controlled by cooling (ice crystals form below 0 degrees Celsius)
- Precipitation from solution: halite (salt) precipitates from excessive evaporation of sea water and increased NaCl saturation. Also, from vapor (snowflakes, ice in hail storm, and native sulfur from volcanic gases)
- Effect of temperature and pressure: temperature and pressure have major effects on crystal habit and density of minerals
Define polymorphs and provide an example.
Polymorphs are two minerals having the same composition but a different crystal structure. For example graphite and diamond are composed of carbon but have different structure.
Describe and define the atomic structure that makes up elements and isotopes.
All matter on Earth and each of the natural elements is made up of atoms.
An atom is the smallest particle into which an element can be divided while this element still retains its own chemical characteristics.
At the center of the atom, the nucleus contains positively charged particles or protons, and neutrons with similar mass but no charge. Quarks are elementary particles forming protons and neutrons. The negatively charged particles or electrons are orbiting the nucleus in shells.
Both the protons and neutrons have a mass that is 1833 times greater than an electron.
The atomic number of an element is the number of protons contained in the nucleus and this atomic number determines what chemical element this atom is (8 for O, 26 for Fe, 6 for C)
The sum of the numbers of protons and neutrons in any nucleus is the atomic mass number of the element, and atoms with different atomic mass numbers (of a given element) are called isotopes of that element.
What are isotopes?
Atoms of a given element have the same atomic number (Z), but with a different mass number (A).
Example, carbon has 3 isotopes (6,7, or 8 N) so C12, C13, C14
List the type of chemical bonds and the bond combination of the most abundant mineral on Earth.
Chemical compounds form when different elements combine together through bonding. Several types of bond exist:
1. Ionic bond: involves the transfer of electrons due to electrostatic attraction. Results in a strong bond
Example: NaCl or halite
2. Covalent bond: involves sharing of electrons between the different elements. Very strong bonds.
Example: diamond (tetrahedral structure)
3. Metallic bond: occurs in metallic minerals where free electrons are moving through the entire network of ions but are not bounded to any ionic pair
Example: gold, silver…
4. Van der Waals bond: weak electrostatic attraction due to off-centering of nucleus positive charges, very weak bonds.
Example: Graphite
Most silicate minerals have a combination of both ionic and covalent bonds
What are minerals grouped based on?
Based on two fundamental characteristics: their internal structure and their chemical composition
List the seven types of mineral groups and describe them along with examples.
- Silicates: most frequent mineral group on earth’s surface. The basic building block is SiO4 called silica tetrahedron.
Silicates are subdivided into groups based on the arrangement of the silica tetrahedra:
a) isolated silicates (simplest structure): consisting of isolated compounds of silicates. Tetrahedra are isolated from each other by cations on all sides.
Example: Olivine
b) chain silicates: silica tetrahedra form long chains by sharing oxygen atoms in chains.
- single chain => pyroxene minerals
- double chain => amphibole minerals
the single and double chains are linked to each other by cations
c) Sheet silicates: silisa tetrahedra are connected to each other in two dimension and form sheets
Example: clays and micas, Muscovite (white mica) and biotite (dark mica)
d) Framework silicates: silica tetrahedra are connected to each other in 3D, all four oxygen are shared
Example: quartz, K-feldspar, Na-feldspar, plagioclase
Write an equation representing simple substitution. State the requirements for this to occur.
Elements that substitute each other must have similar sizes and the same charge.
Elements such as Mg, Fe, and Na, K can substitute each other with very minor adjustment of crystal structure without breakdown or collapse of that structure.
Simple substitution:
Olivine:
Mg1Fe1SiO4 => Fe2SiO4=>Mg2SiO4
(because Fe<->Mg)
Feldspar:
NaAlSi3O8 (albite) =>KAlSi3O8 (orthoclase)
What are the physical properties that can be used to identify minerals?
Color Crystal form Hardness Streak Luster Density (specific gravity) Cleavage/fracture Special properties: magnetism, reaction with acids as HCl, taste, smell,etc.)
What are the physical properties that can be used to identify minerals? Provide description and examples.
- Color: such as quartz = colorless, rose, purple, etc. the color is not specific only for one type of mineral.
- Crystal form: inherent property of a mineral. Crystals of any mineral tend to develop natural crystal faces and assume a specific geometric form.
Example: needle, cubic (such as halite and pyrite crystals), fibrous (asbestos), hexagonal (quartz) crystal form - Hardness: resistance to abrasion
the Moh’s Hard Scale is Talc 1, Gypsum 2 [fingernail], Calcite 3 [copper coin], Flourite 4, Apatite 5 [kinfe blade], Feldspar/ Orthoclase 6 [window glass], Quartz 7 [steel file], Topaz 8, Corundum 9, Diamond 10 - Streak: is the color of the powder of a mineral, which may differ from the actual color of the mineral. Useful for metallic minerals only. Example: hematite looks black, but has a reddish brown streak, quartz (colorless) has no streak, galena has a grey streak
-Luster: quality and intensity of light reflected from a mineral. There is metallic such as pyrite and gold and non-metallic luster such as silky, quartz has a glassy luster, kaolinite has an earthy luster, muscovite has a pearly luster. - Density (specific gravity)
- Cleavage: Smooth planes of weakness along which minerals would split.
=> muscovite has one cleavage plane
=> feldspar has two cleavage planes
=> galena, halite, and calcite has 3 cleavage planes perpendicular to each other
=> halites and galena( sulfides) have cubic cleavages
=> muscovite has one cleavage plane
=> Quartz which has no preferred orientation to break easily and will fracture resulting in an irregular rough surface
=> calcite (carbonates) have rhombohedral cleavages
=> sheet silicates like muscovite and biotite have one cleavage plane occurs between aluminum hydroxide sandwiches
-Fractures: occurs when minerals break along uneven surfaces usually a characteristic of minerals that have equal chemical bonding in all directions - Special properties: magnetism, reaction with acids as HCl, taste, smell, etc.)
Does cleavage represent the internal crystalline structure of the mineral?
Yes, it does
Give examples and define mafic and felisic silicate minerals.
Mafic silicates are rich in Mg and Fe, denser, dark-colored
Example: olivine, pyroxene
Felsic silicates are enriched in the lighter elements such as silicon, aluminum, sodium, potassium, light colored.
Example: quartz (SiO2), feldspars
Give a summary of cleavage in silicates. Include the mineral, chemical formula and number of cleavage planes.
Picture 5 in desktop
Create a table on the type of minerals include the class, defining anion, and example.
Picture 6 in folder
