lec 6; minerals

8/2/2019 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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lec 6; minerals

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