minerals
DESCRIPTION
Minerals. What are Minerals. All the rocks and minerals in the Earth’s lithosphere are made of elements, but not all rocks are minerals . To be classified as a mineral it must be: A solid Naturally occurring Inorganic Have a crystal structure Has a definite chemical composition. - PowerPoint PPT PresentationTRANSCRIPT
Minerals
All the rocks and minerals in the Earth’s lithosphere are made of elements, but not all rocks are minerals.
To be classified as a mineral it must be:1. A solid 2. Naturally occurring3. Inorganic4. Have a crystal structure5. Has a definite chemical composition.
What are Minerals
There about 4000 known minerals, however of all the elements in the Earth’s crust, only a mere eight make-up 98.5% of the crust total mass. Of those eight elements, more 90% of the minerals are compounds containing only two.
1. Oxygen – 46.6% 5. Calcium – 3.6%2. Silicon – 27.7% 6. Sodium – 2.8%3. Aluminum – 8.1% 7. Potassium – 2.6%4. Iron – 5% 8. Magnesium – 2.1%
Minerals
The formation of minerals is a process known as crystallization.There are three main ways minerals crystallize:
1. Magma Process2. The Pressure Process3. Crystallization from solution
How do minerals Form?
Convection currents deep in the Earth’s mantle cause magma to rise and begin to cool. As the magma cools, atoms, molecules, and ions arrange themselves into regular, repeating patterns and bond forming various crystals.
Magma Process
1. Pressure chemically breaks down the rock
2. Heat and pressure change the rock’s properties without melting the rock
3. The atoms, ions, and molecules recombine to form new minerals
Pressure Process
When water cools or evaporates, the particles of dissolved minerals come together again and crystallize.
Crystallization From Water
Every mineral has a unique set of physical properties that are used to identify it. These properties include:
1. Color2. Luster3. Hardness4. Streak5. Cleavage 6. Fracture7. Density8. Specific Gravity
Mineral Identification
Color is the easiest of all properties to observe however, it is the least reliable.
Color
Luster describes the way a mineral surface reflects light. Lusters include:
1. Metallic2. Nonmetallic3. Greasy4. Dull5. Earthy6. Glassy7. Pearly
Luster
Metallic
Hardness is a mineral’s resistance to being scratched.Mineralogist Friedrich Mohs devised a numeric scale to determine the hardness of a mineral.
Hardness
The streak of a mineral is the color of its powder. Streak is obtained by rubbing the mineral on a streak plate.
Streak
Cleavage is a mineral’s tendency to split along smooth, flat surfaces.
Cleavage
Fracture occurs when a mineral breaks along rough or irregular surfaces.
Fracture
Special type of fracture that occurs in glassy type minerals.
Conchoidal Fracture
Many minerals have similar densities however, very high or low densities can be used to identify certain minerals.
Examples: Pumice: .64 g/cm3
Platinum: 21.5 g/cm3
Formula:
Density
A mineral’s specific gravity is the ratio of its dry mass to the mass of an equal volume of pure water. In general, the specific gravity of a mineral tells you how many times denser the mineral is than pure water.
Formula:
Specific Gravity = ______Dry Mass______ (Dry Mass) – (Wet Mass)
Specific Gravity
Some minerals have unusual characteristics that can be used to identify specific minerals.
Special Mineral Properties
Double Refraction occurs when a single light wave is split into two.Example: Iceland spar
Double Refraction
When certain minerals are exposed to ultraviolet light they will glow.
Fluorescent
Minerals such as calcite and halite have a salty taste.
Taste
Minerals such as lodestone and magnetite are naturally magnetic.
Magnetic
Some minerals such as carnotite and uraninite give off radiation that can be detected using a Geiger Counter.
Radioactivity
Minerals are classified according to similarities in composition. Minerals are classified into four main groups:
1. Silicates2. Carbonates3. Oxides4. Sulfides
Mineral Groups
Silicates are any minerals that contain silicon and oxygen. The basic building block of a silicate is the silica tetrahedron.
Silicates
Properties QuartzSiO2
Color Colorless, rose, amethyst,
smokyLuster GlassyHardness 7Streak WhiteBreak ConchoidalDensity 1.2 g/cm3
Specific Gravity 2.65Crystal Structure
Silica Tetrahedron
Special Properties
-
Major Silicates
The feldspar family makes up approximately 60% of Earth’s crustThe molecular difference between quartz and feldspar is that the silicone atom is replaced by either an aluminum,potassium, sodium, or calcium atom. Feldspar is classified into two main groups:
1. Orthoclase Feldspar: Potassium atom2. Plagioclase Feldspar: Sodium-calcium
atoms
Major Silicates cont.
Properties Orthoclase Feldspar Plagioclase Feldspar
Color Salmon with parallel white fibers
White to gray
Streak White White
Hardness 6 6
Luster Pearly Pearly
Crystalline Structure
Silica Tetrahedron Silica Tetrahedron
Break Cleavage (two directions)
Cleavage (two directions)
Density 2.55-2.75 2.55-2.75
Specific Gravity
2.5 – 2.6 2.5 – 2.6
Orthoclase Feldspar Plagioclase Feldspar
SilicatePyroxene Family: Ferromagnesian
Properties Augite(Ca,Na)(Mg,Fe,Al)
(Al,Si)2O6
Color Brownish greenLuster GlassyHardness 5 – 6.5Streak Greenish grayBreak CleavageDensity 1.2 g/cm3
Specific Gravity 2.65Crystal Structure
Silica Tetrahedron
Special Properties
-
Mineral in the mica family are soft silicates:Muscovite and Biotite are minerals that form flat crystals that cleave in only one direction to form thin sheets.
Silicate
A carbonate is a mineral made of negatively charged carbonate ions bonded to a positive metal ion. Each carbonate is composed of 1 carbon atom and 3 covalently bonded oxygen atoms.
Carbonates
Properties CalciteCaO3
Color Colorless/WhiteLuster GlassyHardness 3 – 3.5Streak WhiteBreak CleavageDensity 2.7 g/cm3
Specific Gravity 2.7Crystal Structure
Rhombohedra
Special Properties
Fluorescent
Acid Test Bubbles
Carbonate
Properties DolomiteCaMg(CO3)
Color WhiteLuster GlassyHardness 3.5 - 4Streak WhiteBreak CleavageDensity 2.48g/cm3
Specific Gravity 2.8Crystal Structure
Rhombohedra
Special Properties
-
Carbonate
Oxides are any mineral containing significant amounts of iron and oxygen.
Sulfides are any mineral containing significant amounts of iron and sulfur.
Oxides and sulfides are used in manufacturing to make steel, medicines, cosmetics, plastics, and paints.Any mineral that can be sold for a profit is known as anore.
Oxides and Sulfides
Properties HematiteFe2O3
Magnetite Fe3O4
PyriteFeS2
Color Black, Red Black, Brown, Gray
Pale to Bright Yellow
Luster Metallic, Earthy Metallic MetallicHardness 5 - 6 5.5 – 6.5 6 – 6.5Streak Red Black Greenish BlackBreak Fracture Fracture ConchoidalDensity 5.255 g/cm3 5.175 g/cm3 4.9 g/cm3
Specific Gravity 5.3 5 5Crystal Structure
Hexagonal Octahedral Cubic
Special Properties
- Magnetic -
Common Oxides and Sulfides
Hematite Magnetite Pyrite