NS3310 – Physical Science Studies

Rocks and Minerals

Rocks Tell Stories

• Limestone

• Basalt

• Breccia

• Gneiss

Key Questions• What is a rock?

• What is a mineral?

• What different kinds of rocks are there?

• How do rocks and minerals form?

• How can you tell them apart?

• Can one type of rock change into another type of rock?

• Can you tell the story of a rock by “reading” its characteristics?

The Story of Limestone

• Limestone forms by the precipitation of CaCO3 from solution in ocean water– What is a solution?– What is a precipitate?

• CaCO3 is an ionically bonded salt– What is an ion?– What is an ionic bond?

Ions• Ions are atoms with more or less electrons than protons

• Complex ions can also form

• Ionic bonds form between ions due to their electrostatic charges

Let’s learn more:

Most elements in the natural environment exist as ions

The Story of Basalt

• Basalt is formed from minerals crystallizing from lava at the earth’s surface

• Basalt is dense and mineral rich

• Basalt’s crystals are very fine-grained

• Basalt is the most common rock in the ocean floor

Distribution of Elements in the Solar System

• Elements in the Sun

• Carbonaceous Chondrites

• Elements in the Earth’s Core

• Elements in the Earth’s Mantle

• Elements in the Earth’s Crust

• Elements in the Earth’s Hydrosphere and Atmosphere

Minerals• Minerals are naturally occurring solids formed through geological processes that

have a characteristic chemical composition, a highly ordered atomic structure, and specific physical properties

• Chemical Composition– Elemental Minerals– Carbonate Minerals (and others with ionic bonds)– Silicate Minerals (and others with covalent bonds)

• Physical Properties– Crystal Structure– Cleavage and Fracture– Streak and Color– Luster– Hardness– Specific Gravity– Special Properties

What Holds Silicate Minerals Together?

• We’ve already seen that carbonate minerals form from ionic bonds, but what holds silicate minerals together?

• Silicate minerals are held together by covalent bonds

Let’s learn more:

The Story of Granite• Granite is an intrusive igneous rock

• Granite is composed of silicate minerals (feldspar, quartz, mica, and horneblende)

• Granite is coarse-grained because the crystals formed slowly

• Most of the earth’s continental crust is made of granite

• Most of this granite formed as intrusions into the earth’s crust

Igneous Rocks• Intrusive

– Granite– Diorite– Gabbro– Porphyry

• Extrusive– Basalt– Andesite– Glass

• Scoria• Obsidian• Pumice

• Pyroclastic– Tuff– Rhyolite

The Story of Gneiss• Gneiss is a metamorphic rock

• This means that it is altered from existing rock but was not completely melted

• The minerals in a gneiss have re-crystallized and formed light and dark bands due to heat and pressure exerted on the rock

• Gneiss has many stories

Rock Cycle• Igneous rocks are formed from magma

cooling in the earth’s crust or lava cooling on the surface.

• Sedimentary rocks are formed from the weathered pieces of existing rock.

• Metamorphic rocks are formed by the recrystallization of existing rocks.

• All rocks are susceptible to weathering and erosion.

• All rocks are also susceptible to metamorphism.

• All rocks can be subducted and re-melted (though the continents preserve rocks formed throughout earth’s history because they float higher in the mantle than do the oceans).

• The rock cycle is a continuous process!

You can Use Texture and Mineral Composition to Identify Rocks

• Igneous Rocks– Intrusive– Extrusive– Pyroclastic

• Sedimentary Rocks– Clastic– Chemical– Bioclastic

• Metamorphic Rocks– Foliated– Unfoliated

Types of Rocks• Igneous

– Intrusive– Extrusive– Pyroclastic

• Sedimentary– Chemical

• Precipitates and Evaporites• Fossiliferous

– Clastic• Sorted• Unsorted

• Metamorphic– Foliated– Unfoliated

Sedimentary Rocks

• Sediment Formation– Mechanical and Chemical Weathering

• Sediment Transport– Water, Ice, Wind and Gravity

• Sediment Deposition– Weathering and Erosion– Environment of Deposition

Clastic Sedimentary Rocks

• Unsorted– Conglomerate– Breccia

• Sorted– Quartz Sandstone– Arkose– Graywacke– Siltstone– Shale

Chemical Sedimentary Rocks

• Precipitates– Limestone– Dolomite– Travertine– Chert

• Evaporites– Gypsum– Halite

Metamorphic Rocks• Metamorphic Processes

– Recrystallization– Rotation

• Regional Metamorphism

• Contact Metamorphism

• Foliated Metamorphic Rocks– Slate– Phyllite– Schist– Gneiss

• Unfoliated Metamorphic Rocks– Marble– Quartzite

Key Concepts• Minerals are naturally occurring elements and compounds in the earth.

• Rocks are combinations of minerals (or in some cases a single mineral) that form the earth’s crust.

• Rocks that form from magma, lava or pyroclastic material are igneous rocks.

• Rocks that form from sediments produced by chemical and physical weathering are called sedimentary rocks.

• Rocks that form by remineralization of existing rocks are metamorphic rocks.

• Processes that form and change rocks comprise the rock cycle.

• The characteristics of rocks tell their stories!