Unit 1.2: EVM

Rock cycle

The rock cycle describes the processes through which the three main rock types transform from one type into another.

Igneous rocks

Igneous rocks are made from liquid magma

• Magma cools to form solid rock

• Mineral crystal sometimes present, size depends on cooling

• No fossil present

What are the three types of igneous rocks?

Extrusive, Intrusive, Plutonic

Examples of igneous rocks

Sedimentary Rock

• Made from other rock fragments

• Rock fragments become buried and increased pressure forms a rock

• No crystal

• Fossil maybe present

Examples of sedimentary rocks

Metamorphic rocks

• Metamorphic rocks are created by existing rocks when heat or pressure 

• Mineral crystals are present

• No fossils

Examples of metamorphic rocks

Common metamorphic rocks

Lava

Magma that reaches the earth’s surface

Question 1: What stone results when magma cools and crystallizes slowly within the Earth's crust?

Plutonic or intrusive rocks

Question 2: What rocks are metamorphic rocks built or created from?

From existing rocks

Why are sedimentary rocks very compact and hard

Due to the sediments being buried deeply layer by layer.

minerals vs rocks

• Minerals have the same chemical composition throughout. ( Graphite – C ). 

• Rocks are simply a combination of 2 or more of different minerals.

Mineral

Naturally formed, inorganic solid that has a definite crystalline structure

Question: What is in magma?

Minerals

Magma composition

Silicates

Minerals that are made of a silicon—oxygen bond. 90% of all minerals are silicates.
e.g. quartz, mica and feldspar

Earth’s most common minerals

Feldspar, quartz, mica

Feldspar

• Makes up 60% of the Earth’s crust.

• Hardness = 6

• Pearly luster.

• Usually pink or white.

Quartz

• 2nd most common mineral.

• Hardness = 7

• Glassy luster.

• Many colors, usually white.

Mica

• Breaks in sheets.

• Hardness = 2.5

• Flat, shiny sheets

Mineral must be:

• Naturally occurring made from non-living things,
  (Fossils come from dead organisms, so they aren’t minerals.)

• Not man-made

Minerals must be: (cont.)

• Solid

• Have a fixed shape and volume

• Never living- inorganic

Minerals must be: (cont.)

• Have a definite crystal structure

• particles line up in a regular, repeating pattern.

• flat sides called faces, that meet at sharp edges and corners.

Minerals must be: (cont.)

• A definite chemical composition

• Always contains certain elements in the same proportion.

❖ Almost all minerals are compounds, (two or more different elements chemically joined).

Basic mineral requirements

• All minerals must:

  •  Occur naturally in nature

  • Inorganic solid

  • Crystal structure

  • Definite chemical composition

Question 1: Are pearls minerals?

Pearls are not minerals because it does not have a distinctive crystal structure and it is formed by the action of a living organism.

Question 2: Is coal a mineral

Coal is not a mineral because it comes from organic materials.
Coal forms when dead plants and animals are compressed underground for millions of years.

Question 3: Is salt a mineral?

Salt a crystalline mineral that is composed primarily of sodium chloride (NaCl); a chemical compound.

Properties used to identify minerals

• Color — what color is it?

• Luster — way a mineral shines 

• Streak — does it leave a streak if rubbed on a white tile?

• Hardness — use Mohs’ Hardness scale from 1 to 10.

• Cleavage — how does it break?
  

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Color

• Most easily observed property.

• Least useful for ID.

• Minerals can have impurities or come in a variety of colors.

• Helpful for elimination.

Luster

• The way a mineral reflects light.

  
  Either metallic or nonmetallic. 

  𝑵𝒐𝒏-𝒎𝒆𝒕𝒂𝒍𝒊𝒄:

• Vitreous — Glassy.

• Pearly — like a pearl

• Resinous — Waxy, plastic

• Adamantine — very hard to break

• Dull — no reflection

.𝒎𝒆𝒕𝒂𝒍𝒊𝒄:

• Metallic — like a metal

Streak

• The color of its powder

• Rub on white tile to find the streak

Streak of metallic mineral is usually the color of the mineral.

Streak of non-metallic mineral is usually colorless or white.

Hardness

•     A measure of how easily a mineral can be scratched
  

  Hardest mineral

• diamond
  

  Softest mineral

• talc

Mohs Hardness Scale

Cleavage

• The way a mineral breaks.  

• May be none, 1, 2, 3, 4, or 6 dir

• Or an absence of cleavage is called fracture.

Fracture

Absense of cleavage

Properties of Minerals

Density

• Minerals will have a certain density regardless of the size of the sample.

• Each mineral has its own density called specific gravity

Acid Test

Putting acid on the mineral to see if there is a reaction (effervescing).

Special Properties

• Magnetism

• Glowing under UV light

• Double refraction

Double refraction

Splits lines in two

Question 1: Are bricks rocks

No, bricks are not rocks. Rocks are formed naturally through erosion and weathering.

Question 2: Are glaciers rocks?

Yes, glaciers are rocks. They are naturally occurring (not man-made), solid, and they can form large deposits. Snow, lake ice, and glaciers fit the definition

Rocks classification

• Texture

• Grain

• Minerals

• Color

• Origin of rocks
  

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Texture

• Texture is how a rock looks and feels

• texture in rocks is determined by the size, shape, and pattern of a rocks grains.

Grain

• Size, is it large or small?

• Shape, smooth, rough, round, jagged?

• Pattern – rows, waves, swirls, beads or random patterns

Mineral composition

Rocks are made up of more than one mineral

Color

Color rocks come in all sorts of colors

How are rocks formed

• magma

• erosion and layering

• heat and pressure

Origin of igneous rocks

Igneous rocks are formed from the cooling of magma or lava

Origin of sedimentary rocks

Sedimentary rocks are formed from other rocks that are broken into small particles and moved by erosion (wind or water)

• The particles are squeezed or cemented together 

• Rocks are layered

Origin of metamorphic rocks

Metamorphic rocks are formed from other rocks

• Rocks have been pushed deep into the earth’s crust

• Pressure from the earth above and heat from the mantle below cause them to change shape, color, grain and crystal structure

Rock identification chart