Topic 6MINERALS

Mr. Rocco

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Mineral?• Naturally occurring in the earth• Solid• Definite chemical composition• Atoms arranged in a specific

pattern• Inorganic not from once living

organisms

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(See ESRT pg. 11)• 8 elements which make up approx. 99% of

earth's crust by mass

MINERALS ARE IDENTIFIED BY CHEMICAL AND

PHYSICAL PROPERTIES!

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TOP 4 Elements1. Oxygen (O) -- 46 %2. Silicon (Si) -- 28 %3. Aluminum (Al) -- 8 %4. Iron (Fe) -- 5.5 %

88% total•OVER 3000 known minerals…but 95% of crust is made of only 20 most common minerals

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Most Minerals • Elements combined by attraction of

charges (protons and electrons)

• compound formsExamples:

• Quartz Si + O

•Halite (salt) Na + Cl

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Some Minerals

• NATIVE made of only 1 element

Examples: • Gold (Au)• Silver (Ag)• Copper (Cu)

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AND SULFURH

OBSERVATIONS:

• USED TO IDENTIFY A MINERAL BASED ON ITS PHYSICAL PROPERTIES

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1. Color:•not good property to use to ID

(ex:Quartz comes in many different colors)

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2. Luster:

• the way light reflects from the surface

• Metallic (Looks like polished metal/ aluminum foil wrap)

• Non Metallic(majority of minerals…dull, earthy, glassy)

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PYRITE

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Minerals Species: Galena.

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3.Streak:• Color of powder after mineral

is rubbed against white porcelain plate (streak plate)

Galena is gray but leaves a black streak

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4.Hardness:

•mineral's resistance to being scratched

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Moh's Hardness Scale:1. (softest)Talc2. Gypsum3. Calcite4. Fluorite5. Apatite6. Orthoclase feldspar7. Quartz8. Topaz9. Corundum10.(hardest) Diamond

GLASS= 5.5

Fingernail= 2.5Penny= 3.5

Streak Plate= 7

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5.Cleavage:• the way a mineral breaks along

weak zones and forms SMOOTH,FLAT surfaces

• due to internal arrangement of atoms!!!

• 6 basic crystal shapes

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6.Fracture• when minerals do not break

along zones of weakness1. Earthy (Hematite)2. Fibrous (splinters) (asbestos)3. Conchoidal (curved/scooped)

(obsidian)

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7.Specific Gravity:• IS THE SAME AS DENSITY LIKE 3

G/CM 3 BUT WITH NO UNITS… • ( SO A MINERAL WITH A SPECIFIC

GRAVITY OF 3 IS SAYING IT HAS A DENSITY OF 3 G/CM 3)

• Most common rocks SG= 3• Gold SG= 20

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ACID TESTDilute HCL BUBBLES

CALCIUM CARBONATE in Calcite

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How a Mineral Forms:

1. Crystallized from hot molten material (“magma soup”)600-1200O C at depths of 30 km or more– Slow Cooling= LARGE

CRYSTALS!

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2. Evaporation of water Halite (NaCl)

3. Precipitated from water due warming of sea water:iron oxides, carbonates

4. Heat and pressurerecrystallized new mineral formsMETAMORPHISM

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Atomic Structure

One of the basic atomic structures of the more than 3000 known minerals is the

silicon-oxygen tetrahedron

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(Si + 0 ) FORM THE LARGEST GROUP OF

MINERALS….the SILICATES

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TYPES OF SILICATES• Tectosilicates

(framework silicates)• Phyllosilicates

(sheet silicates)• Nesosilicates

(single-linked silicates)

• Inosilicates - Chain Silicates

• QUARTZ

• MICA

• OLIVINE• Pyroxene

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CRYSTAL SHAPES

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Why do different crystals have

different shapes and sizes?

This depends on 2 factors: 1.The internal symmetry of the

crystal, and 2.The relative growth rates along the

various directions in the of the crystal.

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CRYSTAL SHAPE AXES LENGTHS AXIAL ANGLES1. CUBIC All equal All 902. TETRAGONAL a=b not = c all 903. HEXAGONAL a=b not = c 2 are 90, one 1204. ORTHORHOMBIC all unequal all are 905. MONOCLINIC all unequal two are 906. TRICLINIC all unequal none are 90

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b

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Cubic crystals are not always cube shaped! There are many that are shaped like octahedrons (eight faces), and some that are shaped like dodecahedrons (10 faces).

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Tetragonal crystals are shaped like cubic crystals but are longer in one direction making shapes like double pyramids and prisms.

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Zircon

Orthorhombic crystals are often shaped like rhombic prisms or dipyramids (two pyramids stuck together). They often look a bit like tetragonal crystals except that they are not square in cross section (when you look at the crystal on end).

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Quartz

Hexagonal crystals often look like six-sided prisms. When you look at the crystal on end, it looks like a hexagon shape in cross section.

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Sulfur

Monoclinic crystals look like tetragonal crystals that have been skewed. Often, they form prism shapes and double pyramids.

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Feldspar

Triclinic crystals are sometimes very strange shapes! They are usually not symmetrical from one side to the other.

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Albite

Gem?• a crystalline rock that can

be cut and polished for jewelry

• Beautiful and valuable!!!!

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January Garnet

February Amethyst

March Bloodstone or Aquamarine

April Diamond

May Emerald

June Pearl or Moonstone

July Ruby

August Sardonyx or Peridot

September Sapphire or Lapis Lazuli

October Opal or Pink Tourmaline

November Topaz or Citrine

December Turquoise or Zircon

BIRTHSTONES