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Mineral – naturally occurring, inorganic, solid that has crystal structure and
definite chemical composition (most are compounds)
Identifying minerals – each has its own specific properties we can use for this
1. Hardness – (1812 Friedrich Mohs) - Mohs hardness scale ranks minerals
softest to hardest – pg. 50
2. Color – can be used for only a few
3. Streak – the color of a minerals powder – rub mineral on an unglazed tile
4. Luster – how a mineral reflects ling from its surface
5. Density – each has its own density –
6. Cleavage and Fracture – how a mineral breaks apart
 Cleavage – splits easily along flat surfaces evenly – due to atom
arrangement
 Fracture – describes how one looks when it breaks apart in an
irregular way – jagged points, uneven fractures
7. Special properties – such as fluorescence, radioactivity, magnetism, etc.
Properties and Uses of Minerals – chart pg. 52
Formation of minerals – two major ways
1. Crystallization of melted materials
 The cooling of magma or lava
 Magma – cooling underground slowly forms large crystals
 Lava – cooling on surface quickly forms small crystals
2. Crystallization of materials dissolved in water
 Magma heats water underground – dissolve minerals form
solutions in water – cools – elements and compounds leave solution
and crystallize as minerals – often forms veins or channels of
minerals
Minerals can also form as water evaporates on the surface – ancient seas
deposits table salt over millions of years
Earth’s crust is common rock-forming minerals combined in various types of
rocks. Less common and rare minerals are not distributed evenly
throughout the crust – instead in concentrated deposits
Mineral Resources – minerals are the source of metals, gemstones, and other
materials used to make many products
1. Gemstones – hard, colorful mineral with brilliant or glassy luster,
valued, relatively rare, jewelry
2. Metals – aluminum, iron, copper, silver – useful b/c they can be
stretched, flattened or hammered without breaking
3. Other useful minerals – in foods, medicines, fertilizers, and building
materials – talc, fluorite, kaolin, quartz, gypsum
Ore – a rock that contains a metal or an economically useful mineral which are
mined in one of three ways – strip mines, open-pit mines, and shaft mines
Ores must be processed before the metals they contain can be used – through
process called smelting – ore melted to separate the useful metal from other
elements the ore contains – alloy it two or more metals mixed together
Rocks
Rocks – a mixture of minerals and other materials, including minerals
Geologists observe rocks and identify them by color, texture, and their mineral
composition
1. texture – the size, shape and pattern of the rock’s grains
 gain size – course-grained easy to see/fine-grained harder to see
 grain shape – some small like sand-some due to the crystals in rock –
some due to the fragments of other rock within the rock
 grain pattern – some grains in pattern of layers – some swirling
patterns – some random
 no visible grain – those that cooled very quickly – smooth, shiny
texture like glass
2. mineral composition – rock cut into thin slices – shine light through them –
testing with acid to determine mineral composition
3. origin – three major classifications of rock each due to a different manner of
formation
 igneous rock – forms from the cooling of molten rock – magma
(below) or lava (surface)
 sedimentary rock – forms when particles of other rocks or remains of
plants and animals are pressed and cemented together – layers below
surface
 metamorphic rock – formed when existing rock is changed by heat,
pressure, or chemical reactions – most forms deep underground
Igneous Rocks (ignis “fire) – made from mineral crystals from magma/lava
 Orgin – where formed –
1. Extrusive – formed from lava on the surface (basalt) much of crust,
including ocean floor – texture is usually fine-grained with small
crystals or glassy
2. Intrusive – formed from magma hardened beneath surface (granite)
crust that makes up continents/mountain ranges – coarse gain large
crystals
 Texture – depends on size/shape of mineral crystals
1. fine grained - rapid cooling lava with small crystals
2. coarse grained – slow cooling magma with large crystals
3. glassy – no visible grain
4. porphyritic – forms when intrusive rocks cool in two stages – magma
cools forming large crystals then cooling slows down and smaller
crystals form – they look large crystals scattered in smaller crystals
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Color – silica (oxygen+silicon) determines color to large degree
1. low amounts of silica = dark colored rocks like basalt
2. high amounts of silica = light colored rocks like granite
3. color can change due to mineral content
Uses – many are hard, dense and durable – tools and building materials
Sedimentary Rocks
 Orgin – forms from particles (sediment) deposited by water and wind due to
erosion and/or deposition. Sand grains, mud, pebbles are some of the
sediment that form it.
1. Compaction – over millions of years layers build up and press down
on layers underneath them – squeezing together to form sedimentary
rock
2. Cementation – while compaction is taking place – minerals in rock
slowly dissolve in water and these dissolved minerals crystallize and
glue particles of sediment together
 Types of sedimentary rocks – clastic, organic, and chemical rocks
1. Clastic – forms when rock fragments are squeezed together (shale,
sandstone)
2. Organic – forms where remains of plants/animals are deposited in
thick layers (coal, limestone)
3. Chemical – forms when minerals dissolved in a solution crystallize
(rock salt)
Metamorphic Rocks (meta “change”, morphosis “form”)
 Origin – heat and pressure deep beneath the surface can change any rock
into metamorphic rock – extreme pressure/heat can change appearance,
texture, crystal structure, and mineral content.
 Types of metamorphic rocks – foliated and nonfoliated
1. foliated – grains arranged in thin parallel layers or bands (slate,
schist)
2. nonfoliated – grains arranged randomly (marble, quartzite)
Rock Cycle (diagram pg. 95)
Forces inside Earth and at the surface produce a rock cycle that builds, destroys,
and changes the rocks in the crust. It is a series of processes on and beneath the
surface that slowly change rocks from on kind to another
In one example of a pathway of the rock cycle, igneous rock granite formed beneath
Earth’s surface millions of years ago. Then the forces of mountain building slowly
pushed the granite upwards, forming a mountain. Over millions of years, water and
weather began to wear away the mountain’s granite. Particles of granite broke off
the mountain and became sand. Streams carried the sand to the ocean.
Over millions of years, layers of sand built up. The processes of compaction and
cementation formed the particles into sandstone, a sedimentary rock. As more and
more sediment piled up on the sandstone, pressure on the rock increased. The
rock became hot. Heat and pressure changed the sandstone into the netamorphic
rock quartzite. Metamorphic rock can be melted and the molten material can form
new igneous rock. The process can begin again.
Rock and Mineral Chemistry
Minerals
1. A characteristic of minerals is a definite chemical composition
2. Most minerals are a compound, meaning more than one element
substance
3. A specific mineral, no matter where found on Earth, will always
contain the same chemicals in the same ratio: Quartz: I part Silicon / 2
parts Oxygen
4. An element is comprised of a single atom and therefore a pure
substance
5. Some minerals appear in nature as an element and not a compound:
such as copper, silver, or gold
Rocks
1. Made up of mixtures of minerals and other materials, however some
rocks
only contain one mineral. But unlike minerals, there is no definite
chemical
ratio of minerals within a rock.
2. Using color, texture, and mineral composition geologists can classify
rocks
according to origin, or where and how it was formed.
3. A thin slice of rock, viewed under a microscope, can reveal the size and
shape of the minerals and thereby the types of minerals within the rock
4. Testing with acid determines if the rock contains compounds called
carbonates. Testing with magnets detects the element iron or nickel.