Rocks: Mineral Rocks: Mineral mixturesmixtures

RocksRocks Rock – A solid Rock – A solid

mixture of one or mixture of one or more minerals.more minerals.

The Rock CycleThe Rock Cycle The process by which one rock type changes into The process by which one rock type changes into

another. another. http://www.learner.org/interactives/rockcycle/http://www.learner.org/interactives/rockcycle/

Sedimentary RocksSedimentary Rocks Rocks that form when sediments are Rocks that form when sediments are

compacted and cemented together. compacted and cemented together.

Metamorphic RocksMetamorphic Rocks Rocks that forms Rocks that forms

when the texture when the texture and composition and composition of a preexisting of a preexisting rock changes by rock changes by heat and heat and pressure pressure produced deep produced deep within the Earth.within the Earth.

Igneous RocksIgneous Rocks Rocks that form from cooling of Rocks that form from cooling of

magma and lava both inside and magma and lava both inside and on the surface of the Earth.on the surface of the Earth.

CompositionComposition The minerals a rock is made of The minerals a rock is made of

determines its composition.determines its composition. Example – Granite typically has 10% Example – Granite typically has 10%

Biotitie Mica, 35% Quartz and 55% Biotitie Mica, 35% Quartz and 55% Feldspar.Feldspar.

However, there are classifications of However, there are classifications of Granites that have different amounts of Granites that have different amounts of each of these minerals. each of these minerals.

Composition cont.Composition cont.

Texture The texture of a rock is determined The texture of a rock is determined

by the sizes, shapes and positions of by the sizes, shapes and positions of the grains which it is made of.the grains which it is made of. Fine grained – silt or clay particlesFine grained – silt or clay particles Medium Grained – sandMedium Grained – sand Coarse Grained - pebblesCoarse Grained - pebbles

Fine GrainedFine Grained

Fine grained siltstoneFine grained siltstone

Medium GrainedMedium Grained

Medium grained SandstoneMedium grained Sandstone

Coarse GrainedCoarse Grained

Coarse Grained ConglomerateCoarse Grained Conglomerate

Igneous RocksIgneous Rocks Rocks formed when magma and lava Rocks formed when magma and lava

solidifysolidify IgneousIgneous comes from the Latin word comes from the Latin word

for “fire”.for “fire”. InIntrusive – igneous rocks from when trusive – igneous rocks from when

magmamagma cools cools belowbelow the Earth’s surface. the Earth’s surface. ExExtrusive – igneous rocks that form from trusive – igneous rocks that form from

lavalava cooling on the cooling on the surfacesurface of the Earth of the Earth

IntrusiveIntrusive, or plutonic, igneous rocks , or plutonic, igneous rocks form when magma cools slowly form when magma cools slowly below the Earth's surface. Most below the Earth's surface. Most intrusive rocks have large, well-intrusive rocks have large, well-formed crystals. Examples include formed crystals. Examples include granite, gabbro, and diorite. granite, gabbro, and diorite.

                  

Granite

                  

Gabbro

                  

Diorite

ExtrusiveExtrusive igneous rocks form when igneous rocks form when magma reaches the Earth's surface magma reaches the Earth's surface cooling quickly to form lava. Most cooling quickly to form lava. Most extrusive (volcanic) rocks have small extrusive (volcanic) rocks have small crystals. Examples include basalt, crystals. Examples include basalt, rhyolite, and andesite. rhyolite, and andesite.

                 

Basalt

                     

Rhyolite

                 

Andesite

Mafic RocksMafic Rocks Mafic is used for silicate minerals, Mafic is used for silicate minerals,

magmas, and rocks which are magmas, and rocks which are relatively high in the heavier relatively high in the heavier elements. The term is derived from elements. The term is derived from using the MA from magnesium and using the MA from magnesium and the FIC from the Latin word for iron. the FIC from the Latin word for iron. Mafic minerals are usually dark in Mafic minerals are usually dark in color and have relatively high color and have relatively high specific gravitiesspecific gravities

Felsic RocksFelsic Rocks Felsic, is used for silicate minerals, Felsic, is used for silicate minerals,

magmas, and rocks which have a magmas, and rocks which have a lower percentage of the heavier lower percentage of the heavier elements, and are correspondingly elements, and are correspondingly enriched in the lighter elements, such enriched in the lighter elements, such as as silica and oxygensilica and oxygen, aluminum, and , aluminum, and potassium. The term comes from FEL potassium. The term comes from FEL for feldspar and SIC, which indicates for feldspar and SIC, which indicates the higher percentage of silica. the higher percentage of silica.

Intrusive Intrusive igneous igneous rocks are rocks are dense and dense and hard and hard and withstand withstand weathering weathering and erosion and erosion well. well.

Sedimentary rock FormationSedimentary rock Formation Sedimentary rock – grains of sand Sedimentary rock – grains of sand

and sediment are eroded by and sediment are eroded by weathering forming thick layers that weathering forming thick layers that are eventually cemented together. are eventually cemented together.

They are commonly formed on the They are commonly formed on the ocean floor and other low areas.ocean floor and other low areas.

The most common rock found on the The most common rock found on the Earth’s surfaceEarth’s surface

WeatheringWeathering

DepositionDeposition

Forming the ocean floorForming the ocean floor

LimestoneLimestone rocks rocks are sedimentary are sedimentary rocks that are made rocks that are made from the mineral from the mineral calcite which came calcite which came from the beds of from the beds of evaporated seas evaporated seas and lakes and from and lakes and from sea animal shells. sea animal shells. This rock is used in This rock is used in concrete and is an concrete and is an excellent building excellent building stone for humid stone for humid regions. regions.

ConglomerateConglomerate rocks rocks are sedimentary rocks. are sedimentary rocks. They are made up of They are made up of large sediments like large sediments like sand and pebbles. The sand and pebbles. The sediment is so large sediment is so large that pressure alone that pressure alone cannot hold the rock cannot hold the rock together; it is also together; it is also cemented together cemented together with dissolved with dissolved minerals. minerals.

Grand CanyonGrand Canyon

Painted DesertPainted Desert

Metamorphic RocksMetamorphic Rocks Metamorphic rocks are formed deep Metamorphic rocks are formed deep

within the Earth.within the Earth. ““MetaMeta” in Latin means ” in Latin means changechange. .

““MorphMorph” in Latin means ” in Latin means shapeshape. . Thus, metamorphic means a physical Thus, metamorphic means a physical

change to a rock caused by heat and change to a rock caused by heat and pressure.pressure.

Contact MetamorphismContact Metamorphism

When When surrounding rock surrounding rock comes in contact comes in contact with magma but with magma but does not melt does not melt they often they often change to harder change to harder metamorphic metamorphic type rocks.type rocks.

The lava flow exposed in this road cut The lava flow exposed in this road cut near Alturas, California, has baked the near Alturas, California, has baked the mud beneath it into brick-red shale, a mud beneath it into brick-red shale, a case of contact metamorphism. case of contact metamorphism.

Regional MetamorphismRegional Metamorphism Rocks that are Rocks that are

typically altered in typically altered in composition, texture, composition, texture, or internal structure or internal structure by extreme heat and by extreme heat and pressure over a large pressure over a large area during mountain area during mountain formations or formations or subduction. subduction.

Foliated Metamorphic RocksFoliated Metamorphic Rocks     The generally-crude layering or The generally-crude layering or

foliation of many metamorphic rocks is foliation of many metamorphic rocks is due to the intense directional pressure due to the intense directional pressure they experience they experience

Usually along a convergent plate Usually along a convergent plate tectonic boundary. tectonic boundary. 

  Flat mineral crystals and fragments Flat mineral crystals and fragments gradually become oriented gradually become oriented perpendicular to the directions of perpendicular to the directions of pressure.  pressure. 

Foliated rocksFoliated rocks

More Foliated rocksMore Foliated rocks

jaspilitejaspilite, which , which consists of consists of alternating alternating bands of red bands of red chert (jasper; chert (jasper; cryptocrystalline cryptocrystalline quartz - SiO2), quartz - SiO2), red hematite red hematite (iron oxide - (iron oxide - Fe2O3), and Fe2O3), and silvery-gray silvery-gray specular specular hematite (iron hematite (iron oxide - Fe2O3).oxide - Fe2O3).

Chert