W2 Earth Materials and Processes
Test is easy, can be done anywhere, convenient for field geologists
Advantages of Mohs Scale
Minerals
Building blocks of rocks
Hardness
A measure of the resistance of a mineral to abrasion
Crystalline Formation
Atoms are arranged in an orderly, repeating patterns
Igneous rocks, sedimentary rock, metamorphic rock
Basic rock types
Natural, Inorganic, Have Crystalline Formation, Definite Chemical Composition
Characteristics of Minerals
Silicates, Oxides, Sulfates, Sulfides, Carbonates, Native elements, Halides
Classification of Minerals by Chemical Composition
Sulfides
Classification of Minerals by Chemical Composition contains sulfur anions that combine with 1 or more ions
Carbonates
Classification of Minerals by Chemical Composition that contains carbonate anion combined with other elements
Halides
Classification of Minerals by Chemical Composition that contains halogen elements combined with one or more elements
Oxides
Classification of Minerals by Chemical Composition that contains oxygen anion combined with 1 or more metal ions
Silicates
Classification of Minerals by Chemical Composition that contains silicon and oxygen
Sulfates
Classification of Minerals by Chemical Composition that contains sulfur and oxygen anions
Evaporites, precipitates, bioclastics
Classifications of non-clastic sedimentary rocks
Hardness, streak, acid test
Common mineral identification test
Phosphorescence
Continues to glow even without UV light
Foliated metamorphic rocks
Created from regional metamorphism
The scale is qualitative, it cannot be used for accurate hardness test
Disadvantages of Mohs Scale
Crystal form or habit
External shape of a crystal, which reflects the internal structure of the crystal. It is the natural shape of the mineral before cleavage forms
Fossil assemblages and stratification
Features of sedimentary rocks
Color
First impression in minerals but are not very reliable
Non-clastic sedimentary rocks
Formed from Evaporation and precipitation from solution or lithification of organic matter
Igneous rocks
Formed from solidification of molten rock material
Volcanic or extrusive igneous rock
Formed from solidified lava near the surface of the earth through fast cooling or crystallization due to the huge variance in the temperature between earth's surface and underneath it
Plutonic or intrusive igneous rock
Formed from solidified magma underneath the earth through gradual lowering of temperature that cause slow cooling or crystallization
Sedimentary rocks
Formed through accumulation, compaction, and cementation of sediments at surface conditions
Metamorphic rocks
Formed through the transformation of preexisting rocks through the process of metamorphism
Pyroclastic rocks
Fragmental rocks usually associated with violent or explosive type of eruption
Metallic mineral
Generally opaque and exhibit a resplendent shine similar to a polished metal
Friedrich Mohs
German geologist/mineralogist who designed a hardness scale called Mohs Scale of Hardness
Fluorescence
Glows under UV light
Number of cleavage directions
How is cleavage described
Metamorphism
Involves changes in the physical and chemical properties of rocks in response to heat, pressure, and/or chemically-active fluids
Solidification
Involves formation of crystalline solids called minerals
Non-foliated metamorphic rocks
It is formed by contact metamorphism
stratification or layering
It results to a change in grain size and composition
Double refraction
Looking through the mineral, you see "double"
Pressure
Main factor of regional metamorphic rocks
Heat and reactive fluids
Main factors if contact metamorphism
Mohs Scale of Hardness
Measures the scratch resistance of various minerals from a scale of 1 to 10
Natural
Naturally-occurring and come from natural processes
Inorganic
Not alive or was never alive
Regional metamorphism
Occurs in areas that have undergone considerable amount of mechanical deformation and chemical recrystallization during orogenic events, which is commonly associated with mountain belts
Contact metamorphism
Occurs when pre-existing rocks come in contact with magma
Piezoelectric
Produces electricity when applied with pressure
Color, streak, luster, hardness, crystal form, cleavage, specific gravity, others
Properties of minerals
Magnetism
Property of being attracted to magnets
Cleavage
Property of some minerals to break along specific planes of weakness to form smooth, flat surfaces. These exist because the bonding of atoms making up the mineral happens to be weak
Minerals
Solid, inorganic substances that are present in nature and has a definite chemical composition
1. Magnetism 2. Double Refraction 3. Fluorescence 4. Phosphorescence 5. Piezoelectric
Special properties of minerals
Luster
The quality or intensity of reflected light exhibited by the mineral
Specific gravity
The ratio of the density of the mineral and the density of water. Indicates how many times more the mineral weighs compared to an equal amount of water
Fossil assemblages
The remains or traces of plant's and animals that are preserved in rocks
Streak
The true color of a mineral in powder form. Inherent in almost every mineral and is a more diagnostic property compared to color
Metallic and non-metallic
Two kinds of minerals
Plutonic or intrusive igneous rock, and volcanic or extrusive igneous rock
Types of igneous rocks
Contact metamorphism, regional metamorphism
Types of metamorphic rocks
Clastic sedimentary rocks, non-clastic sedimentary rocks
Types of sedimentary rocks
Non-metallic mineral
Vitreous (glassy), adamantine (brilliant/diamond-like), resinous, silky, pearly, dull (earthy), greasy, among others
Clastic sedimentary rocks
Volcanic in origin and they have the components of grains, matrix, and cement. They are classified based on particle size
Native elements
these are minerals that form as individual elements such as metals or inter-metals, semi-metals, and nonmetals