minerals - science departmentatisciencedepartment.weebly.com/uploads/5/4/8/6/54867073/minerals.pdfg)...

MINERALSCHAPTER 4 SECTION 1

What are minerals?, video

https://www.youtube.com/watch?v=tnwRqlpWo7Y

MINERALS

Vocabulary

• Mineral

• Silicate

• Silicon-oxygen tetrahedron

• Carbonates

• Oxides

• Sulfates and sulfides

• Halides

• Native elements

• Streak

• Luster

• Crystal forms

• Hardness

• Mohs scale

• Cleavage

• Fracture

• density

WHAT ARE THE FIVE CHARACTERISTICS OF A MINERAL?

Video: https://www.youtube.com/watch?v=8a7p1NFn64s

1. A mineral is a naturally occurring, inorganic solid with an

orderly crystalline structure and a definite chemical

composition.

a)Examples of minerals in everyday life:

• Salt

• Lead in pencils contains graphite

• Make-up or powders have mineral talc

• dentist’s drill has minerals so it can drill through tooth enamel

• Quartz is the main ingredient used in windows and drinking

glasses


For an Earth material to be considered a mineral, it

must have the following characteristics:

1.Naturally occurring, formed by natural geological

processes

2.Solid substance, Minerals are solids within the

temperature ranges that are normal for Earth’s surface.


3.Orderly crystalline structure, the atoms or ions are

arranged in an orderly and repetitive manner.


4. Definite chemical composition, chemical compounds made up of

two or more elements.

a) Gold and silver are exceptions

b) Mineral quartz is 2 oxygen atoms for every one silicon atom (SiO2)

5. Generally considered inorganic, Most minerals are inorganic

crystalline solids found in nature.

a) Salt (halite) is inorganic

b) Sugar is a crystalline structure but is organic

WHAT PROCESSES RESULT IN THE FORMATION OF MINERALS?

There are four major processes by which minerals form:

crystallization from magma, precipitation, changes in pressure and

temperatures, and formation from hydrothermal solutions.

1. Crystallization from Magma, Magma is molten rock. It forms deep

within Earth. As magma cools, elements combine to form

minerals such as feldspar, quartz, muscovite, and hornblende.

The first minerals to crystallize from magma are usually those

rich in iron, calcium, and magnesium.


2. Precipitation. The water in Earth’s lakes, rivers, ponds, oceans,

and beneath it surface contains many dissolved substances. If

this water evaporates, some of the dissolved substances can

react to form minerals. Changes in in water temperature may also

cause dissolved material to precipitate out of a body of water.

Two common minerals that form in this way are limestone caves

and halite and calcite.


3. Pressure and Temperature. Some minerals, including talc and

muscovite, form when existing minerals are subjected to changes

in pressure and temperature. An increase in pressure can cause

a mineral to recrystallize while still solid. The atoms simply

rearranged to form more compact minerals. Changes in

temperature can also cause certain minerals to be come

unstable. Under these conditions, new minerals form, which are

stable at the new temperature


4. Hydrothermal Solutions. A hydrothermal solution is a very hot

mixture of water and dissolved substances. Hydrothermal

solutions have temperatures between about 1000C and 3000C.

When these solutions come into contact with existing minerals,

chemical reactions take place to form new minerals. Also, when

such solutions cool, some of the elements in them combine to

form minerals such as quartz and pyrite.

HOW CAN MINERALS BE CLASSIFIED?

1. Silicates, the most common groups of minerals on Earth. Silicon and

oxygen combine to form a structure called silicon-oxygen tetrahedron.

a) Tetrahedron, consists of one silicon atom and four oxygen atoms,

providing the framework of every silicate mineral. Except for a few

silicate minerals, such as pure quartz (SiO2), most silicates also contain

one or more other elements.


b) Silicon-oxygen bonds are very strong.

c) Some minerals, such as olivine, are made of millions of single tetrahedra.

d) In minerals such as augite, the tetrahedra join to form single chains.

e) Hornblende has double chains of tetrahedra

f) Micas has tetrahedra that join to form sheets.

The internal

structure of a

mineral affects it

properties


g) Silicate minerals can often provide scientists with clues about the

conditions in which minerals are formed by:

i. Most silicate minerals crystalize from magma as it cools; this can happen

near the Earth’s surface or at great depths. The place of formation and

chemical composition of the magma determine which silicate minerals will

form.

ii. Silicate minerals formed at Earth’s surface when existing minerals are

exposed to weathering. Clay minerals, which are silicates, form this way.

iii. Other silicate minerals form under the extreme pressures that occur with

mountain building.


2. Carbonates, are minerals that contain the elements

carbon, oxygen, and one or more other metallic

elements.

a) Calcite (CaCO3), most common carbonate mineral

b) Dolomite, limestone, marble


3. Oxides, are minerals that contain oxygen and one or

more other elements, which are usually metals.

a) Rutile (TiO2), forms as magma cools beneath Earth’s

surface; titanium oxide

b) Corundum, (Al2O3), form when changes in temperature

and pressure occur.; aluminum oxide

c) Hematite, (Fe2O3), forms when existing minerals are

exposed to liquid water or moisture in the air; iron oxide


4. Sulfates and sulfides, are minerals that contain the

element sulfur.

a) Anhydrite (CaSO4) and gypsum (CaSO4 + 2H2O) form

when mineral-rich waters evaporate

b) Galena (PbS), sphalerite (ZnS), and pyrite (FeS2) often

form from thermal, or hot-water solutions


5.Halides, are minerals that contain a halogen ion plus one

or more other elements.

a) Halogens are elements from Group 7A of the periodic

table. This group includes the elements fluorine (F) and

chlorine (Cl).

b) Halite (NaCl), table salt

c) Fluorite (CaF2) is used in making steel; forms when salt

water evaporates


6.Native elements, are minerals that only contain one

element or type of atom.

a)Gold (Au), silver (Ag), Copper (Cu), sulfur (S)

b)carbon (C); diamonds, graphite (pencils)

c)Some native elements form from hydrothermal

solutions.

PROPERTIES OF MINERALS

VOCABULARY

Streak

Luster

Crystal form

Hardness

Mohs scale

Cleavage

density

WHAT PROPERTIES CAN BE USED TO IDENTIFY MINERALS?

Video: https://www.youtube.com/watch?v=32NG9aeZ7_c

https://www.youtube.com/watch?v=32NG9aeZ7_c


1.Color

a)Small amounts of different elements can give the

same mineral different colors.


2.Streak

a)Streak is the color of a mineral in its powdered form.


3.Luster

a)Luster is used to describe how light is reflected from

the surface of a mineral.

b)Minerals that have the appearance of metal are said to

have a metallic luster

c)Nonmetal luster are described as vitreous or glassy,

pearly, silky, earthy, adamantine or brilliant (like a

diamond)


4. Crystal form

a.Crystal form is the visible expression of a mineral’s internal

arrangement of atoms.

b.Every mineral has a crystal from based on one of six distinct

crystal systems (slide 36)

c.When a mineral forms slowly and without space restrictions, it

will develop into a crystal with well form faces – sides, top and

bottom.

d.Crowding results in an intergrown mass of small crystals. None

of these crystals shows its crystal form.


5. Hardness

a)Hardness is the measure of the resistance of a mineral to being

scratched.

b)You can find this property by rubbing the mineral against

another mineral of known hardness. One will scratch the other,

unless they have the same hardness.

c)Mohs scale consists of 10 minerals arranged from 10 (hardest)

to 1 (softest)


6. Cleavage

a)Cleavage is the tendency of a mineral to cleave, or break, along

flat, even surfaces.

b)In the atomic structure of a mineral, some bonds are weaker

than others. These weak bonds are places where a mineral will

break when it is stressed.


7. Fracture

a)Minerals that do not show cleavage when broken are said to

fracture.

b)Fracture is the uneven breakage of a mineral.

c)Quartz breaks into conchoidal fracture

d)Asbestos break into splinters or fibers.


8. Density

a)Density if the property of all matter that is the ratio of an object’s mass to its volume.

b)Many common minerals have densities between 2 and 5gm/cm3.

c)Some metallic metals have densities that are often greater than rock-forming minerals. For example Galena, and gold

d)Density can be used to determine the purity or identity of some minerals.

WHAT ARE SOME DISTINCT PROPERTIES OF MATTER?

1. Some minerals can be recognized by other distinctive properties.

a)Talc feels soapy

b)Graphite feels greasy

c)Metallic minerals, such as gold, silver and copper, can be shaped

d)Magnetite and hematite are magnetic

e)When a piece of transparent calcite is place over printed material, the lines appear double (double refraction)

f) Streaks of a few minerals that contain sulfur smell like rotten eggs

g)A droplet of hydrochloric acid will cause carbonate minerals, such as calcite, to fizz

WHAT ARE SOME DISTINCT PROPERTIES OF MATTER?

1.

minerals - science departmentatisciencedepartment.weebly.com/uploads/5/4/8/6/54867073/minerals.pdfg)...

Documents