Transcript Minerals - BHS Library

Minerals
The Stuff that Rocks are made of
PowerPoint Notes created by S. Koziol
Date : 9/1/2013 Revised : ?/?/??
Objectives
What is a mineral?
Define a mineral.
Describe how minerals
form.
Identify the most
common elements in
Earth’s crust.
Potash
Liroconite
Sphalerite
Gold
Minerals
Minerals always exist in a solid(1) form.
Salt
Minerals (continued)
A naturally occurring(2) substance is one that is
made by natural processes. Thus, a substance
developed in a lab, such as a synthetic
diamond, cannot be considered a mineral. An
inorganic substance is one that is not alive nor
has ever been alive. Therefore coal, formed by
an organic process, is not a mineral.
Minerals - composition
Although a few minerals are composed of single
elements, most are made from compounds.
(Mg,Fe)2SiO4
SiO2
Olivine
Quartz
Solids with a specific chemical composition.(3)
Mineral - crystals
Crystal – Solid in which the atoms are arranged
in repeating patterns(4)
Mineral – crystals (continued)
A mineral can take the shape of one of the six major
crystal systems.
Magma
Magma - Molten material found beneath Earth’s
crust.
Minerals - formation
Minerals can form when differences in density
force magma upward into cooler layers of
Earth’s interior.
Minerals - magma
When compounds in cooling magma no longer
move freely, they may interact chemically to
form minerals.
Minerals – formation (continued)
Mineral crystals may begin to precipitate out of
a solution that has become saturated.
Always have a
scale in science
images
Minerals – formation (continued)
Minerals form from cooled magma and from
elements in solutions.
Earth’s Crust – abundant elements
The most abundant elements in Earth’s crust are
silicon and oxygen.
Silicates
Silicate - Mineral that contains silicon and oxygen. These make up the
most common mineral group.
Silicates
Sub-classification based on tetrahedral structure
Non-Silicates
Natives elements – only one element
Sulfides - with a sulfur; tellurium, arsenic, or selenium
Oxides – O22Halides - (fluorine, chlorine, iodine, and bromine) is the main anion.
Carbonates – [CO3]2Sulfates – [SO4]2Phosphates – [PO4]3-
http://ruby.colorado.edu/~smyth/min/minerals.html
Common Minerals
The most common minerals, feldspar and
quartz, are silicates.
Think about it
If you took random samples
of minerals from several
locations, which type of
mineral would you likely
have more of—oxides,
silicates, or carbonates.
Why?
There likely would be more
silicates than other types
because 96 percent of the
minerals in Earth’s crust
are silicates.
Known Minerals
There are at least 4,900 known minerals in
Earth’s crust.
Ore
Minerals that contains a useful substance that
can be mined for profit.
Peacock Ore - copper
Argentite - silver
Ore - continued
The classification of a mineral as an ore may
change once it has been mined.
Ore - continued
Ores near Earth’s surface generally are obtained
from open-pit mines.
“525 m deep, 1200 meters in
diameter. The air zone within
this mine is closed for
helicopters - a few accidents
occurred when they were
“sucked in” by downward air
flow…”
Gem
Valuable mineral prized for its rarity and beauty
Quiz Break
Remember there was a reason for taking those class notes . . .
Objectives
Of Identifying minerals
Classify minerals
according to their
physical and chemical
properties.
Identify different
types of minerals.
Discuss how minerals
are used.
Potash
Liroconite
Sphalerite
Gold
ID-ing Minerals
Minerals can be identified based on their physical
and chemical properties.
Physical
Chemical
ID-ing Minerals - luster
Silver, gold, and copper have shiny surfaces and
thus are said to have metallic luster.
Silver
Gold
Copper
Luster is described as either metallic or nonmetallic.
ID-ing Minerals - streak
A mineral’s streak rarely changes, but
sometimes does not match its external color,
even if it is weathered or its external color
varies slightly.
ID-ing Minerals – trace elements
Trace elements in a mineral can affect the color
or the value of mineral.
ID-ing Minerals – luster & streak
Luster is the way a mineral reflects light from its
surface, while streak is the color of a mineral
when it is broken up and powdered. Both are
tests used to identify a mineral.
ID-ing Minerals – specific gravity
Geologists commonly use specific gravity as a
measure of density for accurate identification
of a mineral.
ID-ing Minerals – density vs.
specific gravity
Density is the ratio of the mass of a substance
divided by its volume. Specific gravity is the
most common measure of density. It is the
ratio of the weight of a substance to the
weight of an equal volume of water.
ID-ing Minerals - hardness
Mohs scale is used to compare the hardness of
minerals.
Finger nail ~2.2
Glass, steel knife ~ 5.5
Streak plate 7
ID-ing Minerals - cleavage
Mica has perfect cleavage in one direction; it
breaks in sheets.
ID-ing Minerals - fracture
When flint and opals break, they have a unique
fracture with arclike patterns.
ID-ing Minerals – cleavage &
fracture
Minerals with cleavage
split easily and evenly
along one or more
planes, while minerals
with fracture break
unevenly along jagged
edges. Both describe
how minerals split due
to their atomic
arrangements.
ID-ing Minerals – hardness &
texture
Hardness is a measure of how easily a mineral can be
scratched, while texture describes how a mineral feels.
Both are tests used to identify a mineral.
ID-ing Minerals - inorganic
A mineral, such as salt, is naturally occurring but
inorganic, in contrast to sugar, which comes from
plants.
The most reliable way to identify a mineral is by
using a combination of several tests.
cleavage - Property of splitting along one or more
flat planes evenly and easily
fracture - Property of breaking with rough or
jagged edges
hardness - Measure of how easily a mineral can be
scratched
streak - Color of a mineral when it is broken up and
powdered
luster - The way a mineral reflects light from its
surface
Why do geologists usually use a combination of
tests to identify a mineral?
Some minerals have characteristics similar to
other minerals. Therefore, more than one test
may be necessary to accurately identify the
minerals.
ID-ing Minerals – specific gravity
Mineral
Specific Gravity
Chemical Formula
Breakage Pattern
Gold
Apatite
Pyrite
Garnet
19.3
5
5.2
3.5–4.3
Hackly
Uneven fracture
Uneven fracture
Conchoidal fracture
Beryl
Corundum
2.75
4
Au
Ca5(PO4)3(F, OH, Cl)
FeS2
(Mg, Fe, Ca) 3
(Al2Si3O12)
Be3Al2Si6O18
Al2O3
Uneven fracture
Fracture
If the volume of the sample of beryl equals the volume of the sample of gold,
how many times greater is the mass of the gold sample than the mass of the
beryl sample?
SG 19.3 ÷ 2.75 = 7.02 times greater
ID-ing Minerals - Hardness
Mineral
Gold
Apatite
Pyrite
Garnet
Beryl
Corundum
Color
Metallic gold
Blue, green
Metallic pale brass, gold
Red, deep red, brown
Bluish green, green
Red, deep red
Hardness
2.5–3
5
6–6.5
6.5–7.5
7.5–8
9
ID-ing Minerals - Hardness
Mineral
Gold
Apatite
Pyrite
Garnet
Beryl
Corundum
Color
Metallic gold
Blue, green
Metallic pale brass, gold
Red, deep red, brown
Bluish green, green
Red, deep red
Hardness
2.5–3
5
6–6.5
6.5–7.5
7.5–8
9
Which mineral can scratch at least one of the green stones?
pyrite
Which mineral can scratch neither green stone?
gold
Which mineral can scratch at least one of the red stones?
beryl
Which mineral can scratch neither red stone?
apatite
Which mineral can scratch only one of the green stones?
garnet
Quiz Break 2
Remember there was a reason for taking those class notes . . .