6. Minerals and Rocks 6.1 Minerals are all around us 6.2 Rocks form in different ways 6.3 Natural processes break down rocks 6.4 Geologic maps show Earth’s surface features

6.1 Minerals are all around us Before, you learned: –Earth is made of layers –Earth’s outermost rocky layer is the crust Now, you will learn: –About the characteristics of minerals –How minerals are classified into groups –Which mineral group in most common

Warm-up Questions Latitude is a distance in degrees ________ or _________ of the _________ (T/F): Relief maps use contour lines to show features Geographic information systems display data in _____ to build maps

Minerals and rocks are part of daily life Wires carrying eletric current are made of copper – a mineral! Table salt (halite) – a mineral! The Earth’s crust is made of rocks – almost all rocks are made of minerals!

Minerals Minerals are not the same as rocks A rock has only two of the characteristics –Solid and forms in nature –A rock usually has two or more types of minerals Minerals are always made up of the same materials in the same proportions –Quartz crystal has 2 Oxygen atoms for every silicon atom

Minerals A mineral is (generally) an inorganic, naturally occurring, organized crystalline structure composed of a single chemical compound or element. A rock is (generally) a natural solid composed of multiple crystals of one or more minerals –Although many rocks contain visible crystals of individual minerals, a rock itself does not have an overall crystalline structure.

Minerals have four characteristics 1. Form in nature 2. Are solids 3. Have a definite chemical makeup 4. Have a crystal structure Examples: copper in the wires that carry electricity, table salt (halite) Is water a mineral? Is ice? Can minerals be found in rocks? " A naturally occurring, inorganic material of constant chemical composition and a definite crystalline structure."

Minerals – 1. Formed in Nature C an be formed by processes that do not necessarily involve living organisms A few minerals can be produced by organisms as part of shells or bones Haline forms when water evaporates in a hot shallow part of the ocean Granite forms when molten rock cools

Minerals – 2. Solids Definite volume and a rigid shape –Volume: amount of space an object takes up

Minerals – 3. Definite Chemical Makeup Specific combination of atoms of certain elements –Element: a substance that contains only one type of atom –Atom is the smallest particle an element can be divided into –Most minerals contains more than one element – compounds – elements in specific proportions

Halite – NaCl Copper - Cu

Minerals – 4. Have a Crystal Structure Crystal: solid in which the atoms are arranged in an orderly, repeating 3-D pattern Two minerals can have the same chemical composition but different crystal structures ge_build.cfm?id=resour_ch2&u=2#%23

Diamond and graphite are both made of Carbon The individual atoms have the same properties, but are in different arrangement giving the substance very different properties – different crystal structure

Minerals are grouped according to composition Grouped on the basis of chemical makeups Most common group is silicates –Contain oxygen silicon – most common in Earth’s crust – joined together Rock-forming minerals –The 30 minerals that make up most of the crust –Silicates make up 90% of the rocks in the crust Quartz, feldspare, and mica –2 nd most common: Carbonates (carbon and oxygen) - calcite

Rocks are made of minerals Minerals –must have the four previously mentioned characteristics –Always made of the same elements in the same proportions, have an orderly crystal structure A rock only has two of the four: –It is a solid and forms naturally –Rocks are usually made of two or more minerals –The proportion of different minerals in a certain type of rock may vary –The minerals in a rock can be all jumbled together –Only a few types of rocks are made of only one type of mineral Ex: limestone (calcite) –A few contain no minerals at all Ex: obsidian (made of natural glass – no crystal structure) Ex: Coal (remains of ancient plants)

Math in Science Each mineral makes up a certain proportion, or fraction, of a granite sample –You can compare mineral amounts by expressing each mineral’s fraction as a percentage To change a fraction to a percentage, you must find an equivalent fraction with 100 as the denominator –1/5 to percent? First, divide 100 by the denominator 5 = 20 Then multiply the numerator and denominator by 20 = 20/100 = 20%

Minerals in a Granite Sample MineralFraction of granite sample Percentage of granite quartz1/4 feldspar13/20 mica3/50 Dark minerals1/25