Mineral or not?Which of these is a mineral? Why

or why not?

Rose Quartz

Princess Penny

Garnet

Gene Simmons

Eggs are to cake…Eggs are to cake…What minerals are to rocks.

3 Main Rock GroupsIgneousSedimentaryMetamorphic

Igneous Rocks

Igneous RocksIgneous comes from the Greek word for Fire.

Igneous rocks are formed when hot molten rock crystallizes and solidifies.

Igneous RocksForms from molten material◦magma

Magma is molten rockWhat is magma?

Magma is molten rockWhat is magma?

Mostly oxygen, silicon, aluminum, iron, magnesium, calcium, sodium, potassium, titanium, and manganese.◦As well as melted rock, crystals, bits

of unmelted parent rock and dissolved gases.

Igneous RocksIf magma cools quickly:◦There is less time for crystals to formCrystals will be small

Igneous RocksIf magma cools slowly:

◦There is more time for crystals to growCrystals will be larger

2 Types of Igneous RocksBased on where they form:

◦ Intrusive / Plutonic Magma that cools and hardens

below the surface.◦ Extrusive Magma that cools and hardens

above the surface (lava).

Intrusive Igneous Rocks Intrusive or Plutonic rocks form when

molten rock, or magma, is trapped deep within the earth where it slowly cools and solidifies.

The cooling may take thousands or even millions of years.

Since it takes so long to cool, the crystals within the rock may grow relatively large.

Slow cooling, and large crystals create a coarse grained texture.◦ Ex: granite, gabbro, diorite

Igneous RocksIntrusive or Plutonic

Batholith- large igneous intrusionSills – an igneous intrusion parallel to the layers

Lacolith – an igneous intrusion into sedimentary layers

Intrusive Igneous Rocks

Extrusive Igneous RocksExtrusive rocks are formed by

magma that exits the earth(lava).◦Ex: From volcanoes, and fissures.

As magma erupts from the earth it cools very rapidly. There is little time to form large crystals.◦Extrusive rocks are fine grained or

even glassy texture. Ex: basalt, rhyolite, obsidian.

Extrusive Igneous Rocks

Igneous Rocks

Igneous Rock groups2 main groups based on their

chemical composition;MaficFelsic

MaficMafic magmas have relatively low silica (Si) and high Fe and Mg contents.

◦The high Fe and Mg content makes these rocks heavier & darker than felsic types. Mafic magma will cool and crystallize to

produce the volcanic rock basalt and gabbro.

MaficVery Hot lava, rich in iron and

magnesium, low in silica, is fluid and flows like hot tar (highly viscous).◦ Mafic Magnesium

+ Iron Mg + Fe

Mafic rocksMagnesium + Iron (Fe)More easily weathered than

felsic-typesHighly dense/heavyDark colored

◦Ex: basalt, gabbro

Felsic Felsic magmas, have relatively high silica and low Fe and Mg contents.

◦Lighter in weight and color than mafic.

◦Felsic magma will cool and crystallize to produce dacite and rhyolite. Intermediate-composition magmas

will crystallize to produce the rock andesite.

FelsicCooler, gas-poor lava high in silicon,

sodium, and potassium can be either pasty, blocky or flows very slowly (not viscous).◦ Felsic Feldspar +

Silicon Fe + Si

Felsic RocksFeldspar + Si

◦Harder◦Weather last◦Low density◦Lighter color◦Ex: quartz, muscovite, orthoclase

Igneous RocksIf lava is felsic and contains a

high percentage of gases it will be explosive.◦If thick the lava will explode in blocks

or bombs.

Igneous RocksIf lavas are thin and contain few

gases, the flow will be very viscous.◦Smooth, liquidy

How Igneous Rocks are formed

Extrusive Igneous Rocks

What type of igneous rocks are formed here?

http://hvo.wr.usgs.gov/gallery/kilauea/volcanomovies/

What types of igneous rocks would be formed here?