1

Mineral & Rock

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Composition of the Earth

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Element• An element is a substance that cannot be

separated into simpler substances by ordinary chemical means.

• The smallest part of an element that has all the properties of that element is an atom.

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Mineral• A mineral is a naturally occurring

• inorganic

• solid

• definite chemical composition

• crystal structure.

**It must have all five of the characteristics described in this definition.**

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Rocks• A rock is a hard substance composed of

one or more minerals.

• A rock can also be made of or contain naturally occurring substances that do not perfectly fit the definition of a mineral.

• Rocks can be composed of volcanic glass or of opal. Both of these substances lack a crystalline structure.

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Rocks• หิ�นออบซี�เดี�ยน (Obsidian)

• SiO2 ที่� มี�มีลที่�นสู�ง(impurities )

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Bonding• Ionic bond

• Covalent bond

• Metal bond

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Lattices• Atoms in crystals form a repeating pattern

called a Lattice

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Identifying Minerals

Color -Sometimes Distinctive

• Often Unreliable

• Affected By:– Chemical Impurities – Surface Coating – Grain Size – Weathering Fluorite

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Identifying Minerals (Continued)

We Need Properties Directly Linked to Atomic Structure:

• Hardness• Streak• Density• Luster• Cleavage• Crystal Form

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สี�ผงละเอี�ยด (Streak) ขี�ดบนแผ�นกระเบ��อีงที่��ไม่�เคล�อีบ หร�อี แผ�นขี�ดสี�(streak plate)

แร�ฮี�ม่าไที่ต์�

สี�น��าต์าลแดง

สี�ด�า

แคลโคไพไรต์�

ไพโรล�ไซต์�

สี�ขีาว

ที่$ลก� ฟล�อีอีไรต์�

สี�เหล�อีง

อีอีร�พ&เม่นต์�

ซ$ลเฟอีร�

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Hardness•Resistance to Scratching •Directly related to relative strength of atomic bonds

•Scratch Test (Mohs)•Indentation Test (Knoop)

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HardnessTalc

Gypsum

Calcite

Fluorite

Apatite

Feldspar

Quartz

Topaz

Corundum

Diamond

4

2

3

6

5

1

7

8

9

10

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Mohs vs. Knoop Scales

1. Talc: very small 2. Gypsum, Fingernail: 30 3. Calcite, Penny: 135 4. Fluorite: 163

5. Apatite: knife 430 6. Feldspar, Glass: 560 7. Quartz: 820 8. Topaz: 1340 9. Corundum: 2100 10. Diamond: 7000

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Mohs and Knoop scale

http://www.themeter.net/durezza_e.htm

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DensityAluminum: 2.7Pyrite, Hematite, Magnetite: 5.0Galena: 7.5Iron: 7.9Copper: 9Lead: 11.4Mercury: 13.6Uranium: 19Gold: 19.3Platinum: 21.4Iridium: 22.4 (densest material on Earth)

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Luster• Metallic or Nonmetallic is the most

important distinction

• Resinous, waxy, silky, etc. are self-explanatory.

• Vitreous is often used for glassy luster

18 ควอีต์ซ� วาว

แก'ว กาล�นา วาวโลหะ

ความ่วาว (Luster)เป็)นล$กษณะที่��สีาม่ารถพบได'บนผ&วแร�เน��อีงจากการต์กกระที่บและเก&ดการสีะที่'อีนขีอีงแสีง

แสีงต์กกระที่บ

แสีงสีะที่'อีน

วาวแบบอีโลหะ (Non - metallic

luster)

วาวแบบโลหะ

(Metallic luster)

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แนวแต์กเร�ยบ (Cleavage)

ไม่กา

เป็)นล$กษณะรอียแต์กขีอีงแร�ที่��เก&ดขี��นในแนว ระนาบเร�ยบเน��อีงจากโครงสีร'างอีะต์อีม่ภายในผล0ก

รอียแต์ก แบบน��จะขีนานไป็ต์าม่ผ&วหน'าขีอีงแร�

อีอีร�โที่เคลสี

กาล�นา ฟล�อีอีไรต์�

แคลไซต์�

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รอียแต์ก (Fracture) รอียแต์กขีอีงแร�ที่��ไม่�ม่�ที่&ศที่างแน�นอีน และพ��นผ&ว

รอียแต์กไม่�เป็)นระนาบเร�ยบ แต์�ม่�ล$กษณะต์�างๆ ก$น 1 รอียแต์กโค'งเว'า

(Conchoidal) 2. รอียแต์กแบบ

เสี��ยน (Splintery) 3. รอียแต์กหย$ก

แหลม่ (Hackly)

4. รอียแต์ก ขีร4ขีระ

(Uneven)

5. รอียแต์ก เร�ยบ (Even)

ควอีต์ซ� ย&ป็ซ$ม่

ที่อีงแดง

โรโดโครไซต์� คาลซ&โดน�

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Crystal Form• Takes Luck & Practice

• Well-formed crystals are uncommon

• Crystal Classification is somewhat subtle

• From solutions, melts, and vapors

• Evaporation of solvent, cooling, reduction of pressure

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Precipitation of crystals from vapor

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The Crystal Classes

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Geologic Setting •Some minerals occur in all geologic

settings: quartz, feldspar, pyrite

•Some minerals occur mostly in sedimentary settings: calcite, dolomite

•Some minerals occur mostly in igneous settings: olivine

•Some minerals occur mostly in metamorphic settings: garnet, kyanite

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Special PropertiesSome minerals can be identified by

special properties.

• Magnetite is naturally magnetic.

• Fluorite glows under ultraviolet light.

• Halite tastes salty.

• Sulfur smells like rotten eggs.

• Calcite fizzes when hydrochloric acid is added to .

• Uraninite is radioactive.

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Minerals By Class• Minerals can be organized, mainly

according to their chemistry

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Minerals By Class(1)Elements Class: The Metals and their alloys and the Nonmetals. Sulfides Class: The Sulfides, the Selenides, the Tellurides, the Arsenides, the Antimonides, the Bismuthinides and the Sulfosalts. Halides Class: The Fluorides, the Chlorides and the Iodides. Oxides Class: The Oxides and the Hydroxides. Carbonates Class: The Carbonates, the Nitrates and the

Borates.

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Minerals By Class(2)

Sulfates Class: The Sulfates, the Sulfites, the Chromates, the Molybdates, the Selenates, the Selenites, the Tellurates, the Tellurites and the Tungstates (or the Wolframates).

Phosphates Class: The Phosphates, the Arsenates, the Vanadates and the Antimonates.

Silicates Class: The Silicates (the largest class). The Organics Class: The "Minerals" composed of organic chemicals! The Mineraloids: The "Minerals" that lack crystal structure!

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Major Mineral Suites

Elements

Metallic:Au, Ag, Cu

• Not Al, Pb, Zn, Fe, etc.

Nonmetallic: C - Diamond, Graphite

• Sulfur

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Major Mineral Suites

SULFIDES: Dense, Usually MetallicMany Major Ores

• Pyrite FeS2

• Chalcopyrite CuFeS2

• Galena PbS

• Sphalerite ZnS2

• Molybdenite MoS2

Major Cause of Acid Rain

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Major Mineral Suites

HALIDES: Usually Soft, Often Soluble

• Halite NaCl

• Fluorite CaF2

SULFATES: Soft, Light Color

• Gypsum CaSO4

• Barite BaSO4

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Major Mineral Suites

OXIDES: Often Variable, Some Ores

• Hematite Fe2O3

• Bauxite Al(OH) 3 (a hydroxide)

• Corundum Al2O3 (Ruby, Sapphire)

CARBONATES: Fizz in Acid, Give off CO2

• Calcite CaCO3

• Dolomite CaMg (CO3)2

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Carbonates

• Principal Components of limestone and dolostone

• Storehouse for CO2

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Oxide: Hematite

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Hydroxide: Bauxite

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Most Important Mineral Suites :

The Silicate Minerals

• Si + O = 75% of Crust

• Silicates make up 95% + of all Rocks

• SiO4: -4 charge

• Link Corner-To-Corner by Sharing Oxygen atoms

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Silica Structures

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Asbestos

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Silicates

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Tectosilicates - 3-D Networks

• Quartz Feldspars

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Quartz

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Reference• http://mineral.galleries.com/minerals/

by_class.htm

• http://www.johnbetts-fineminerals.

com/jhbnyc/minname.htm

• http://www.geo.sc.chula.ac.th/

Knowledge/Rock%20and%20Mineral.

htm