lec 6; minerals
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MineralsMineral a natural,inorganic solid with
a definite chemicalcomposition and aparticular crystallinestructure.
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WHEN DO WE SAY A MATTE
SUBSTANCE IS A MINERAL_________________
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Requirements to be a miner
It must be formed in nature
mineral must come from the Ecrust and not be man-made (artific
It must be inorganic not ma
living matter (organic matteproduced by living things. (nevelived)
It is a solid must be solid for to form characteristic patterns.
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It has a definite chemcomposition - always contain
same elements in the sproportions. (halite: NaCl)
It has a particular crysta
structure The atoms of a mare arranged in a way that forparticular geometric shape (
hexagonal, monoclinic, etc.).
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Mineral FormationTwo natural processes
minerals:1. cooling of magma
2. precipitation process
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Cooling of Magma (1Hot liquid material called magma fr
asthenosphere moves upward through thcrust.
As the magma moves upward it cools and tin the magma lock into place forming crysta
The rate at which magma cools determines th
the crystals Slow cooling magma = large crystals
Fast cooling magma = small crystals
Examples: olivine, feldspar plagioclase, qu
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Precipitation (2) Minerals dissolved in liquids to form
mixtures called solutions. When the liquid part of the solution
evaporates the minerals are left beh
Definition of evaporates phase change whewater turns to water vapor by the heat energySun.
Examples of minerals formed by precipitation:Halite (NaCl) ; Gypsum (CaSO4)
C
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Mineral CompositionMost minerals share chemical similarities and can be grouped into six ma
MineralGroup
Composition Exam
Silicates Si + O + metals QuartCarbonates CO3 + metals CalcitOxides O + metals MagnSulfates SO4 + metals GypsSulfides S + metal GalenHalides Cl + metal Halite
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Crystal Structure (MineralThe crystal shape of minerals is determ
by the arrangement of atoms that makthe mineral. We will study six main c
shape based on 3 or 4 lines thathrough the mineral called axes.
x
y
z
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Cubic - three axes of equal length interse
90-degree angles.
Examples: halite, galena, pyrite
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Tetragonal - same as cubic, but verticaxis is longer or shorter than the others
Examples: chalcopyrite, wulfenite
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Orthorhombic - three axes of diflengths intersect at 90-degree angles.
Examples: olivine, topaz
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Monoclinic - same as orthorhombexcept one axis is tilted.
Examples: mica, gypsum
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Triclinic - three unequal axes intersat titled angles to each other.
Example: plagioclase feldspar
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Hexagonal - three equal horizaxes intersect at 60-degree angles.
vertical axis is longer or shorter others.
Example: pyromorphite
Mineral Identification
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Mineral Identification
Certain physical properties are used to i
minerals. Six main properties will helidentify minerals.
1. Luster 6. Color
2. Streak
3. Specific gravity
4. Cleavage and fracture
5. Hardness
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LusterHow does the mineral reflect l
If the mineral is shiny like a mehas a metallicluster. (galen
All other types of luster are
grouped together, including;pearly, silky, glassy(quartz), dul(pyroxene), and greasythese are
called non-metallic.
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StreakWhat color does a mineral lon a porcelain tile?
The mineral is actually scratcoff on the tile leaving behind
powder of the mineral. This is a very good test beca
the streak is always the sam
even if color varies.
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Cleavage and FractureHow mineral break?
A mineral that breaks along surface of plane, has cleava
A mineral that has unevensurfaces when it breaks, has
fracture.
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Hardness - How well does themineral resist scratching?
Using Mohs Hardness Scalewe willcompare the relative hardness of
minerals.
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Watch and learn!!!
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Watch and learn!!!
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