Defining the Atom
I.
Atomic Theory
A.
B.
C.
D.
E.
F.
All matter is made up of very tiny particles called atoms
Atoms of the SAME element are chemically alike
The atoms of an element have a definite mass that is
characteristic of the element
The Atoms of different elements have a different
number of protons in their nucleus (so atoms of
different elements have different atomic masses).
Atoms are not subdivided, created, or destroyed in
chemical reactions
Sizes of Atoms: Atomic Radius
1.
Atoms are about 1 X 10-12 m in size…so cannot be seen
(why we call it the atomic “theory”)
What makes elements different?
II.
What is an element?
1.
The atoms of different elements have a
different number of protons in their
nucleus
2.
An element is a substance that
cannot be broken down to any
simpler substance; made up of all
the same atoms each with the same
number of protons in the nucleus
3.
Examples: Hydrogen has just one
proton in it’s nucleus, Lithium has 3;
Berillium has 4; Sodium has 11.
4.
The number of protons in the nucleus
is called the atomic number!
Structure of the Atom
III. Structure of the Atom:
1.
2.
All atoms are composed of subatomic particles called
electrons, protons, and neutrons
Electrons, protons, and neutrons are different in terms of
their mass, electrical charge, and location in the atom
IV. Protons and neutrons have the same mass, while electrons
are much lighter.
V. Protons have a positive charge, neutrons are neutral (no
charge) and electrons have a negative charge
VI. Protons and neutrons are found in the center of an atom
(nucleus), while electrons are attracted to the protons on
the outside of the nucleus (opposite charges attract)
I. Minerals
• All minerals are made up of single elements or
compounds.
• Element = a substance that cannot be broken
down to any simpler substance; made up of
atoms
• Atom = smallest part of an element; has all the
properties the element has but cannot be seen
even with tools
• Compound = substances consisting of more
than one element
Minerals - definition
1. Naturally Occurring
 synthetic substances are not minerals
2. Inorganic
 plant and animal activities (coal, pearls are not minerals)
3. Solids
4. Definite Chemical Composition
5. Crystalline Structure
 a crystal is a regular geometric solid shape; reflects the
ordered internal arrangement of atoms
6. Definite Set of Physical Properties
Physical Properties of Minerals
•
•
•
•
•
•
•
Can be used to identify minerals!
Color
Luster
Streak
Odor
Hardness
Breakage Pattern
– Cleavage
– Fracture
Color
• Very useful property only for
some minerals
• Not useful for other minerals
because:
– 1. Many minerals come in
multiple colors
– 2. One color (such as white)
can be seen in many minerals
– May be used for some of the
obvious minerals that are
almost always one color (sulfur
= yellow)
These are all samples of the same mineral!
Quartz comes in many colors!
These four minerals (and many
others) are all white!
Is color always a useful physical property
for identifying minerals?
•NO!
• But it sure makes looking at
minerals a lot more
interesting!
Luster
Luster...
• The way light shines or glares off the surface
of minerals
• Better than color to identify minerals
• Many types of luster have been described
• Somewhat subjective
• Need to familiarize yourself with terms...
Luster...
• Metallic
– looks like metal in the way the
mineral reflects light (Galena
or Pyrite)
• Non-Metallic
– Does not look like polished
metal, so other terms are used.
Types of Non-Metallic Luster
•
•
•
•
Vitreous - glassy, like glass (quartz)
Resinous - a dull shine, like a resin (amber, olivine)
Waxy - dull shine like candle wax (sulfur, olivine)
Adamantine - brilliant glow, beam of light at a
certain angle (diamond)
• Earthy - no shine at all (bauxite)
• Pearly - looks like pearls when light is reflected off the
minerals surface (opal, garnet)
The way light reflects off the surface of
a mineral (luster) is useful in
identifying the mineral
Galena definitely has a metallic luster
as it looks like polished metal
Graphite may display a
“sub-metallic” luster, as it
looks like dull metal
Quartz has a glassy look, which is
called a “vitreous” luster
Match the luster description with the appropriate
luster term by writing the correct number next to
the term:
Luster Term
Definitions
_______Pearly
1. a brilliant glow at certain angles under
the light; such as diamond
_______Dull (Earthy)
2. shines like reflected glass
_______Vitreous
3. no shine at all even under bright light
_______Waxy
4. glistens like pearls under light
_______Metallic
5. shines like candle wax, a dull glow
_______Adamantine
6. gives off a glare like a gold necklace or
silver bracelet
Streak
• The color of the powder of a mineral obtained by
rubbing the sample across an unglazed porcelain plate
(called a streak plate)
• Most minerals display only one color of streak
• Examples:
– Hematite always has a reddish brown streak, no matter what
color the sample is
– Sulfur has a yellow streak
– Sphalerite has a yellow streak
– Magnetite has a black streak
When checking the streak of a mineral,
be sure to follow these steps:
• Hold streak
plate carefully
with index
finger and
thumb of one
hand
• Hold streak
plate firmly
against desk top
• Rub mineral
across plate
firmly to
powder it
Checking streak...
• Be careful not to
break off the
corners of the
streak plate.
• Some streak plates
have sharp edges
so WATCH OUT!
• Check the color of
the minerals
powder to
determine streak.
Color, Luster, and Streak Quiz!
• Color is the most useful property used to identify a
mineral.
• FALSE! Too many minerals are the same color and
many are white, green, black, etc.
Color, Luster, and Streak Quiz!
• Vitreous is a type of non-metallic luster seen on
minerals that reflect light as glass does.
• True! Vitreous is glassy.
Color, Luster, and Streak Quiz!
• The way a mineral reflects light is called streak.
• FALSE! Luster is the way a mineral reflects light.
Streak is the color of the mineral in powder form.
Color, Luster, and Streak Quiz!
• Determining the streak of a mineral is done by
whacking the mineral with a sledge hammer until it is
pulverized.
• FALSE! Streak is easily determined by rubbing the
mineral across an unglazed porcelain plate.
Color, Luster, and Streak Quiz!
• The streak of a mineral will always be the same as the
mineral color.
• FALSE! Streak is particularly useful when it is
different than the color of the mineral itself.
Hardness of Minerals
• Hardness is the resistance of a mineral to
being scratched
• All minerals are assigned a hardness value
from 1 – 10 based upon “Moh’s Hardness
Scale”
• Hardness is one of the most useful
properties because:
– Resistance of a mineral to being scratched
never changes among different samples of
the same mineral
– Hardness is easily determined using your
fingernail, a glass plate, a steel nail, and
reference minerals
Hardness = the resistance of a mineral to being
scratched
• Mineral Name (Moh’s Scale)
– 1. Talc
– 2. Gypsum
* 2.5 Human Fingernail
– 3. Calcite
– 4. Fluorite
– 5. Apatite
* 5.5
–
–
–
–
–
Typical Uses
body powder
building (wallboard, etc.)
lenses in microscopes
toothpaste
fertilizer
GLASS PLATE
6. Feldspar
7. Quartz
8. Topaz
9. Corundum
10. Diamond
floor tiles (mall floors)
watches, abrasives, etc.
gemstones
abrasives, cutting tools
saws, “a girl’s best friend”
A visual look at Moh’s Hardness Scale
Diamonds are so prized because they are harder than any other
substance, so they are extremely resistant!
Hope Diamond
Diamond particles that are not used as gemstones can be
used in cutting saws, and are able to cut all other industrial
materials.
Hardness - continued…
• Hardness is a very useful property, since a mineral’s
hardness is constant – it is the main way we can
separate “soft” minerals (1-5 on Moh’s scale) from
“hard” minerals (6-10)
• “Hard” minerals such as quartz are used as abrasives
• Fingernail is a 2.5 on Moh’s scale, so can be used to
identify very soft minerals (scratched by fingernail)
• Steel nail is about 5.0 on Moh’s scale
– (softer than glass)
Hardness...
• How do we determine the hardness of a
mineral?
– First, we rub an edge of the mineral across a glass
plate, to see if it scratches the glass. Remember, a
glass plate is about 5.5 on Moh’s hardness scale.
– Once we determine whether the mineral is harder
(scratches) or softer (does not scratch) than 5.5, we
use the reference minerals of Moh’s hardness scale
and other items such as our fingernail, steel nail,
etc. to more accurately determine hardness.
Checking for Hardness...
• Be sure to hold the
glass plate down
firmly on the desk
• Be careful of sharp
edges on the glass
plate!
• Glass can be very
fragile and sharp!
• Wipe mineral
across glass plate
to see if it
scratches the glass
Checking hardness...
• Check to see if the
mineral actually
made a groove in
the glass or just
merely rubbed off
on the glass
• A mineral is
harder than glass if
there is a definite
groove or scratch
in the glass plate.
Hardness of Minerals…
• If the mineral does not scratch glass (less than 5.5),
try to scratch it with your fingernail
– If your fingernail can scratch the mineral, it is also less
than 2.5 on Moh’s scale
– If your fingernail does not scratch the mineral, it is
between 2.5 and 5.0 on Moh’s scale.
• KNOWING THE HARDNESS VALUE WILL
MAKE IDENTIFYING THE MINERAL MUCH
EASIER!!!!
Hardness...
Procedure for Determining a Minerals Hardness
Scratches Glass
Harder Than 5.5
Check against a
piece of feldspar, then quartz
then topaz
then corundum
Does Not Scratch Glass
Softer Than 5.5
Fingernail scratches mineral
Softer than 2.5
Check against talc
then gypsum
Fingernail does not scratch
mineral
Check against calcite
then fluorite, apatite
Breakage Pattern
• 1. Cleavage - the tendency of a mineral to split
consistently along certain planes of weakness
• 2. Fracture - no definite planes of weakness so mineral
just breaks along irregular surfaces
Cleavage...
• Minerals may show one or more planes of
weakness:
–
–
–
–
one plane of weakness = basal (muscovite mica)
two planes of cleavage at 90º (orthoclase)
three planes of weakness at 90º = cubic (halite)
three planes not at 90 º = rhombohedral (calcite)
• You must look carefully for “flat” surfaces
which give off a glare to find the cleavage in a
mineral
• Not always obvious
Cleavage...
• Some minerals such
as mica break apart
along one smooth flat
plane, called BASAL
cleavage.
• This sample has also
been cut into straight
edges.
Cleavage...
Basal cleavage
(muscovite mica)
2 directions of
cleavage at 90º
(feldspar)
Cubic cleavage (galena)
Fracture...
• Conchoidal fracture - irregular breakage surfaces are
somewhat rounded (like the way glass breaks)
– Quartz is noted for its conchoidal fracture
• Hackly fracture - breakage surfaces are jagged (such as
the mineral copper)
• Uneven fracture - some minerals break apart in no
distinguishable pattern.
Fracture...
Hackly
fracture
(copper)
Conchoidal fracture
(Quartz)
Quiz…
• Minerals are mostly man-made.
• False. Minerals are naturally-occurring.
Quiz...
• Minerals usually exhibit a characteristic streak, or
powder color.
• True.
Quiz...
• Moh’s hardness scale is used to determine a mineral’s
luster.
• False! Moh’s scale is used to determine hardness.
Quiz...
• Minerals contain every element on the periodic table.
• False. Minerals are composed of one or several of the
elements, in a specific chemical formula.
Quiz...
• If a mineral shines like metal when reflecting light it
has a metallic luster.
• True.
Quiz...
• The physical properties of minerals are used to
distinguish one mineral from another.
• True.
Quiz...
• Cleavage is the breaking of a mineral along irregular
surfaces.
• False. Cleavage indicates certain planes of weakness
within the mineral which causes the mineral to always
break along those planes.
Quiz...
• When checking for the hardness of a mineral, you
should always check to see if it scratches diamond first.
• False. See if the mineral scratches glass first, then use
your fingernail or reference minerals to more accurately
determine hardness.
Quiz...
• When checking the streak of a mineral, always hold the
streak plate flat on the desk and rub the mineral across
the plate to powder it.
• True
Quiz...
• If a mineral appears like glass when reflecting light it is
said to have an earthy luster.
• False. Vitreous is the term used to describe glassy
luster.
Families of Minerals
• Minerals can be categorized into groups (families)
based upon their composition and physical properties.
• Some minerals consist of only one element, and are
called “Native Minerals”.
– Examples: Gold (Au), Copper (Cu) Sulfur (S) and Diamond
(C) are all Native Minerals
Examples of native minerals:
•
•
•
•
•
Gold (Au)
Silver (Ag)
Copper (Cu)
Sulfur (S)
Graphite or
Diamond (C)
• Platinum (Pt)
Native Minerals
23. Most native minerals have monetary value.
– This means that they are very valuable and are the most
sought after minerals.
24. Most metals are considered native minerals and
usually have multiple uses.
25. Native minerals are known for special physical
properties.
– conductivity (electricity)
– pliability (can be bent into shape)
– durability (very strong)
Non-Native Minerals (Compounds)
26. Most minerals are made up of two or more elements
combined (called compounds).
• The following minerals are all compounds!
•
•
•
•
•
•
Orthoclase (KAlSi3O8)
Gypsum (CaSO4·2H2O)
Quartz (SiO2)
Halite (NaCl)
Calcite (CaCO3)
Pyrite (FeS2)
*****The most common minerals are made of the
most abundant elements in Earth’s crust.
Eight most abundant elements in the Earth’s crust:
ELEMENT (% BY MASS)
1. Oxygen (46.10%)
only
2. Silicon (28.20%)
silly
3. Aluminum (8.23%)
artists
4. Iron (5.63%)
in
5. Calcium (4.15%)
college
6. Sodium (2.36%)
study
7. Potassium (2.09%)
past
8. Magnesium (2.33%)
midnight
Families of Minerals
27. Most minerals are combinations of the most abundant
elements found in Earth’s crust.
28. Oxygen and Silicon combine readily with each other
and with other elements to form a family of minerals
called the Silicates.
29. The silicates are the most common family of minerals
and make up over 90% of all minerals
– This is because Oxygen and Silicon are the most common
elements in Earth’s crust!
Which minerals are silicates?
•
•
•
•
•
•
•
•
•
Orthoclase (KAlSi3O8)
Gypsum (CaSO4·2H2O)
Quartz (SiO2)
Halite (NaCl)
Calcite (CaCO3)
Pyrite (FeS2)
Augite (Mg,FeSiO3)
Olivine (Mg,Fe)2SiO4
Biotite K(Mg,Fe)3AlSi3O10(OH)2
Special Properties of Minerals:
30. Magnetism - the ability to attract a magnet (magnetite,
powder of Ilmenite)
31. Effervescence (reaction with acid) - bubbly reaction in
HCl, “fizzing” (calcite, powder of dolomite)
32. Specific Gravity (Density) - some minerals have
atoms very tightly packed, and feel heavier because
they are more dense! Galena is very dense, calcite is
not
33. Specific Gravity - definition
Specific Gravity = How many times heavier a mineral
is than an equal volume of water. This depends on
it’s density.
• Formula for Specific Gravity
S.G. = weight of mineral in air (g)
(weight in air) - (weight in water)
• Specific gravity answers have no units
• Specific gravity is basically how much more dense
a mineral is than an equal volume of water
Special Properties of Minerals:
34. Labradorescence - the colorful hue seen at certain
angles while the mineral labradorite reflects light; looks
blue-purple
35. Striations - a series of very fine parallel grooves found
on the cleavage surfaces of some minerals (Plagioclase
Feldspars have striations, other feldspars don’t: ex.:
albite, labradorite have striations)
36. Double-refraction - the doubling of images when light
passes through mineral (calcite)
Special Properties of Minerals...
37. Taste - Halite tastes like salt (it is salt)
– DO NOT TRY THIS IN LAB!
38. Odor - Sulfur smells like rotten eggs
– Sometimes the powder of a mineral (streak) has a certain odor
(sphalerite smells like sulfur when streaked)
39. Fluorescence - some minerals give off a specific color
when viewed with an ultraviolet light!
40. Piezoelectricity - emits an electric current when put
under pressure (quartz)
41. Without minerals, life would be very
different! Minerals have many uses...
• Jade altar bowl shown here
• Pottery, jewelry, industry,
electricity
• Quartz alone is used as:
–
–
–
–
an abrasive
in watches (piezoelectricity)
in telephones
many other uses
• Think about all of the minerals we
use in the classroom!
• Think of how many minerals it
takes to make an IPOD or cell
phone!
Mineral Quiz: (true or false)
• All minerals have the same chemical composition?
• False. Each mineral has its own ingredients which can
be determined in a special laboratory.
Quiz cont...
• Minerals occur in only one color?
• False. Some minerals such as calcite and quartz come
in many different colors.
Quiz cont...
• A mineral must be a solid (no liquids or gases).
• True.
Quiz cont...
• Hardness, luster, and streak are physical properties that
are useful in identifying minerals.
• True.
Quiz cont...
• Talc is the softest mineral on Moh’s hardness scale
while diamond is the hardest.
• True.
Quiz cont...
• Hardness is determined by scratching a mineral across
an unglazed porcelain plate.
• False. Hardness is checked by scratching the mineral
against a glass plate and then against reference
minerals.
Quiz cont...
• Cleavage is the ability of a mineral to break along
atomic planes of weakness.
• True.
Quiz cont...
• About 8 elements make up most of the minerals found
on Earth.
• True.
Quiz cont...
• All minerals exhibit some form of cleavage.
• False. Some minerals display no special planes of
weakness and exhibit fracture.
Quiz continued...
• The basic building block of the silicate family of
minerals is called the silicon-oxygen tetrahedron.
• TRUE!
Quiz cont...
• There are six components to the definition of a
mineral:
– Naturally Occurring
– Inorganic
– Solids
– Definite Chemical Composition
– Crystalline Structure
– Definite Set of Physical Properties
• TRUE!
How Are Minerals Formed?
•
Minerals are formed by the process of
crystallization as a result of:
1. Cooling and solidification from magma (liquid rock) (ex:
olivine, plagioclase feldspar, potassium feldspar)
2. Precipitation from water caused by evaporation, or over-
saturation of minerals (ex: halite & calcite)
3. Chemical reactions from pressure and temperature
changes within the Earth (ex: talc, muscovite mica)
4. Chemical reactions from hydrothermal solutions (hot
water & dissolved ions from 100°C to 300°C)
(ex: bornite, chalcopyrite)
How Are Minerals Formed?
• Minerals are formed by the process of crystallization as
a result of:
– cooling and solidification from magma (liquid rock)
– precipitation from water caused by evaporation, chemical
reactions, and temperature changes
– rearrangement of atoms in existing minerals subjected to
conditions of high temperatures and pressures found deep
within the earth
Silicon-Oxygen Tetrahedron...
• The tetrahedron is made up of four oxygen
atoms packed closely around a silicon atom
• The tetrahedron continues outward in all
directions like legos, and combines with other
metal elements to build the different minerals
of the silicate family.
• All of the first 18 minerals in your kits are
silicates, except for calcite, gypsum, and halite.
Silicon-Oxygen Tetrahedron...
• This is a model of
the silicon-oxygen
tetrahedron
• The white balls
represent oxygen
atoms
• The black ball in
the center
represents the
silicon atom.
• Imagine millions
of these linked
together in 3D
Silicon-Oxygen Tetrahedron...
• There are many
models used to show
the silicon-oxygen
tetrahedron.
• The way the
tetrahedrons are
linked and the other
elements it binds with
will determine all the
physical properties of
silicate minerals
Silicon-Oxygen Tetrahedron...
• Silicates include the
minerals quartz,
feldspar, augite, and
hornblende.
• The very different
physical properties
these minerals exhibit
is due to the slightly
different chemical
formulas and how the
silicon-oxygen
tetrahedron is linked!