Post on 03-Jan-2016
transcript
MatterMatter: anything that has mass and
volumeElement: substance composed of
atoms; can not be broken down 10 most common elements in Earth’s crust :
– Oxygen (O) - Silicon (Si)– Aluminum (Al) - Iron (Fe)– Calcium (Ca) - Sodium (Na)– Potassium (K) -Magnesium (Mg)– Titanium (Ti) - Hydrogen (H)
The Structure of an Atom
The nucleus is made up of the protons (positively charged molecules) and neutrons (no charge)– The number of protons and neutrons makes up the
atomic number
The electrons (negatively charged molecules) orbit, or circle, the nucleus.
Atomic number – equals number of protons
Symbol – one or two letter abbreviation
Name – elements common nameAtomic mass weighted average of all
isotopes
What is a Mineral?
All rocks and minerals of Earth’s crust consist of elements
Mineral has the following characteristics:– Occurs naturally– Solid– Has a definite chemical composition– Its atoms are arranged in an orderly pattern– Inorganic (never alive)
4,000 known minerals
Eight most common elements found in in minerals:
Oxygen O - Calcium Ca– Silicon Si - Sodium S– Aluminum Al -
Potassium K– IronFe - Magnesium Mg
Most minerals are compounds
– 2. New minerals also form when existing minerals are transformed by heat, pressure or chemical action
Example: Hornblende Schist
3. Precipitation – solids form from super saturated solutions.
Ex calcite and halite
4. Hydrothermal solutions – dissolved elements react with each other in very hot water causing chemical reactions which form new minerals.
Structure of Minerals
Crystal: a regular geometric solid with smooth surfaces called crystal faces– By definition, all minerals have crystalline structures
(regular, orderly arrangements of atoms)
Crystal Structure:– The angle at which crystal faces meet is
characteristic for each type of mineral and can be used to help identify the mineral
– Six basic types of shapes
Cubic System
Orthorhombic System
Tetragonal System
Triclinic System
Hexagonal Structure
Monoclinic Stucture
Silicates:
Minerals that include compounds of silicon and oxygen.
More than 90% of the minerals in Earth’s crust are silicates
Silica tetrahedron: basic building block of a silicate
– Four oxygen atoms packed closely around a silicon atom
Crystal Structure and Physical Properties
The temperatures at which a mineral melts and vaporizes is individual to that mineral
Significance of crystal structure
Example of the relationship between hardness and crystalline structure: The following two minerals are both pure Carbon.– Diamond: Atoms arranged in tetrahedral
network – hardest natural mineral– Graphite: atoms arranged in sheets of
hexagonal networks – soft and flakes easily
Identifying MineralsMineralogy: study of minerals and
their properties
Minerals can be identified and classified by inspecting them visually and performing simple tests to determine their properties
Identifying Minerals by Inspection
Color the most easily observed propertyLeast useful for mineral ID
– Minerals may have similar colors
– Impurities and other factors can change colors
Testing Mineral Specimens
– Certain characteristics can be tested for.– Streak– Cleavage– Hardness– Specific gravity
StreakThe color of a mineral’s powder
Although the color of a mineral may vary, the streak rarely does
CleavageThe tendency to split along
definite planes– The planes along which the mineral splits
correspond to planes of weak bonds between atoms, ions or molecules
Fracture – If a mineral does not cleave, it fractures. An uneven breakage that can occur anywhere on the mineral.
HardnessHardness of a mineral is its resistance
to being scratched– Diamond: hardest of all minerals– Talc: softest of all minerals
Hardness of a mineral depends on: – arrangement of its ions, atoms or
molecules– strength of the chemical bonds between
them
In most cases, a person can determine the approximate hardness of any common mineral by using your fingernail, a copper penny, a small glass plate and a steel file
Specific Gravity:
ratio of a minerals mass to the mass of an equal volume of water– Tells you how many times denser the mineral is
than water– Use a spring scale to measure
– Buoyancy: tendency of an object to float in water due to the differences in densities b/t the water and the object
Special Properties
Some minerals have unusual characteristics that can help ID the mineral
Taste like salt Magnetic propertiesReacts with HCl
Mineral Groups
SilicatesQuartz:
Chemical Formula: SiO2
Glassy or greasy lusterPure Quartz: colorlessColored Quartz: rose quartz, amethystHardness of 7 Significant component of many types of rocks
FeldsparsMake up about 60% of Earth’s crustShare 3 features:
– two directions of cleavage–Hardness of 6–Pearly luster
Most abundant family of mineralsImportant rock-forming mineralsUsed to manufacture glass and
ceramics
Other silicates
– Pyroxene: cleavage surfaces meet nearly at right angles
– Micas: soft silicates; hardness of 2.5 and perfect cleavage
– Amphibole: complex silicates; long, needlelike crystals
– Olivine: used to make jewelry– Kaolinite: aluminum silicate;
commonly used in ceramics, paints and fiberglass
Carbonates Minerals made of negatively charged
carbonate ions bonded to positive metal ions
All Contain CaCO3 –Calcium carbonate
All will effervesce with Hydrochloric acid HCl
Calcite and Dolomite
Oxides
Mineral consisting of a metal element combined with oxygen
– Hematite and Magnetite
– Sulfides– Mineral consisting of a metal
element combined with sulfur
– Pyrite