2.0 Rocks and Minerals!
A Review of Chemistry!

An atom is the smallest particle of matter
that contains the characteristics of an
element.
2.1 Matter
Elements and the Periodic Table
Elements are the basic building blocks
of minerals.
An element is a substance that cannot
be broken down into simpler substances
by chemical or physical means.
 Over 100 elements are known.
Elements

An element is a chemical made of all the
same type of atoms.

Types of elements (most common in the
Earth’s crust)
◦
◦
◦
◦
◦
◦
◦
◦
Oxygen (O)
Silicon (Si)
Aluminum (Al)
Iron (Fe)
Calcium (Ca)
Sodium (Na)
Potassium (K)
Magnesium (Mg)
Words that Matter…

A substance is a material with a specific
chemical composition.

A compound is a pure chemical substance
consisting of two or more different chemical
substances.

A mixture is a collection of molecules or
atoms of different types.
Rocks and Minerals!
Minerals
A
mineral is a naturally
occurring, inorganic solid with
an orderly crystalline
structure and definite
chemical composition.
 Say
what??????????????
Let’s Break it Down!
 Let’s look at each part of the definition in
detail!

A mineral is a naturally occurring, inorganic
solid with an orderly crystalline structure and
definite chemical composition.
A mineral is a naturally occurring, inorganic solid
with an orderly crystalline structure and definite
chemical composition.
 Naturally
occurring means
that the mineral was made by
natural geologic processes
over time. Minerals cannot be
made by humans!
A Silicon Wafer is not naturally
occurring!!!
A cubic zirconia is also not natural!
A mineral is a naturally occurring, inorganic solid
with an orderly crystalline structure and definite
chemical composition.
 Inorganic
means that it does not
contain carbon.
 There are a few exceptions such
as calcium carbonate (limestone).
Peat (partially decomposed organic
material) is not a mineral because it
is not inorganic=organic!
A mineral is a naturally occurring, inorganic solid
with an orderly crystalline structure and definite
chemical composition.
 Solid
means that the minerals
are solid within normal
temperatures on the Earth!
 Of course, they can be melted or
turned into a liquid if heated up
high enough!
Tar: Not a solid AND has carbon so
not a mineral!
A mineral is a naturally occurring, inorganic solid
with an orderly crystalline structure and definite
chemical composition.
 Orderly
crystalline structure
means that the atoms are
arranged in an orderly and
repetitive manner. There are a
few exceptions to this.
Obsidian (volcanic glass) is
sometimes not considered a mineral
because glass is not a crystal!
A mineral is a naturally occurring, inorganic solid
with an orderly crystalline structure and definite
chemical composition.
 Definite
chemical composition
means that the minerals are
composed of elements that occur
in a consistent ratio.
Halite (NaCl=salt) has a definite
chemical composition!
2.2 Minerals Summary
1. Naturally occurring
2. Solid substance
3. Orderly crystalline structure
4. Definite chemical composition
5. Generally considered inorganic
Breaktime!
2.2 Mineral Formation
How Are
Minerals
Formed???
2.2 Mineral Formation

Minerals form almost everywhere in the
Crust under different conditions.
◦ Some minerals form deep within the Crust
and others are formed in shallow deposits.
◦ Some minerals form in ocean water and some
are made from other minerals that have been
crushed and compressed.
2.2 Mineral Formation

There are four major processes by which
minerals are formed:
◦
◦
◦
◦
Crystallization from magma
Precipitation
Changes in pressure and temperature
Formation from hydrothermal solutions.
2.2 Mineral Formation: Crystalization
Crystallization from Magma

As magma (molten rock) cools, the
elements chemically combine to form
minerals.

Usually the iron, calcium and magnesium
minerals crystallize first. The sodium,
potassium and aluminum minerals will
crystallize next.
2.2 Mineral Formation: Crystalization
When the magma cools, the crystals form.
2.2 Mineral Formation: Precipitation
Precipitation

The water found in oceans, lakes, streams,
and rivers contain dissolved substances in
it. When the water evaporates, some of
the dissolved substances in the water can
crystalize to form minerals.
2.2 Mineral Formation: Precipitation

Limestone and halite (sodium chloride)
are two minerals formed by precipitation.
2.2 Mineral Formation: Pressure/Temp
Pressure and Temperature

When existing minerals are subjected to
extreme (high) pressure and temperatures,
new minerals can form.
Marble
2.2 Mineral Formation: Hydrothermal
Hydrothermal Solution

A hydrothermal solution is a very hot
(between 100⁰ C and 300 ⁰ C) mixture of
water and dissolved substances.

When the solution cools, chemical
reactions can take place to form new
minerals.
2.2 Mineral Groups

Over 3,800 different types of minerals
have been identified and named!

These minerals are classified based on
their composition.

The major classes of minerals on earth
are:
◦ Silicates, carbonates, oxides, sulfates/sulfides,
halides, and native elements.
◦ Can you guess what element each of these
groups contain?
2.2 Mineral Groups: Silicates
Silicates

Silicates are the most abundant mineral
on Earth!

They contain what two elements?

Yes! They contain oxygen and silicon
(usually with other elements too!)
2.2 Mineral Groups: Silicates

Silicates are made from cooling magma
and can occur on the Earth’s surface or
deep within the crust.
2.2 Mineral Groups: Silicates
Examples of Silicates
Clay and Sand
 Quartz
 Mica
 Feldspar

2.2 Mineral Groups: Silicates
Quartz Often Exhibits
Good Crystal Form.
2.2 Mineral Groups: Carbonates
Carbonates!

Carbonates are the second most
common group of minerals.

Carbonates contain carbon, oxygen
(CO32-)and one or more other metallic
element.
2.2 Mineral Groups: Carbonates
Examples of Carbonates
Calcium carbonate (limestone and
marble)
 Dolomite
 Calcite (most common carbonate)

2.2 Mineral Groups: Oxides
Oxides

Oxides are minerals which contain oxygen
plus one or more other elements (often a
metal like iron or copper).

Oxides can be made on the Earth’s surface
or deep within the crust.

Oxides often have the name of the metal
and then the word oxide such as iron oxide
(Fe2O3), copper oxide (CuO2), or aluminum
oxide (Al2O3).
Examples!

Copper Oxide

Iron Oxide
2.2 Mineral Groups: Sulfates-ides
Sulfates and Sulfides

Sulfates and Sulfides contain the element
sulfur
FeS2 (pyrite=fools gold)
2.2 Mineral Groups: Sulfates-ides
Gypsum (sulfate) CaSO4 . 2H2O
2.2 Mineral Groups: Halides
Halides

Halides are minerals that contain a
halogen (fluorine, chlorine, bromine or
iodine) plus one or more other elements.
NaCl
2.2 Mineral Groups: Native Elements

Native elements are minerals of a single
element such as gold, platinum, silver,
carbon
Native Copper
Radioactivity is another special
property
Pitchblende (uranium)
Let’s
Review!!!

1. The color of the powder left behind when the mineral is
scraped across a surface
◦ Streak

2. The way in which light reflects from a mineral’s surface
◦ Luster

3. The tendency of a mineral to break along flat surfaces
◦ Cleavage

4. The tendency of a mineral to break into irregular pieces
◦ Fracture

5. The visible light that reflects off the mineral
◦ Color

6. The ability of a mineral to attract a magnet.
◦ Magnetism

7. The reaction of acid on the mineral
◦ Reaction to HCl/Solubility

8. The light that shines when ultraviolet is shined on a mineral.
◦ Fluorescence

9. A mineral’s resistance to being scratched
◦ Hardness
Gems

Gem Minerals

Diamond
Diamond forms at great depths within the lithosphere, where pressures are in excess of 200 kilobars and temperatures of 800° C or higher. Due to its hardness and resistance to acids
ancient Greeks called it adamas meaning “the invincible”. The rock in which diamonds occur is kimberlite (metamorphosed pegmatite) found in areas of Siberia, South Africa, India,
Zaire, Australia, etc. Most commonly diamonds are found in alluvial deposits, but also mined directly from kimberlite (diamond pipes). Less than 25 % of total world’s production of
diamonds is suitable for gems. The value of diamonds depends on the four “C’s”: color, clarity, cut, and carat weight. The most valuable are colorless and blue-white stones. The
world’s largest diamond is Cullinan, found in South Africa in 1905. Cullinan weighs 3106 carats (1 carat = 0.2 grams). First diamonds were synthesized in 1955 in the United States.

Emerald
Emerald is green color variety of silicate mineral beryl. Most commonly it occurs in igneous rocks (pegmatite and granite) but also in metamorphic rocks (mica schists). The most
valuable emeralds are found in Colombia. Other areas of significant emerald production are South Africa, Zimbabwe, and Russia. Emerald is often considered more valuable than
diamond.

Ruby
Ruby is red color variety of oxide mineral corundum. It occurs in metamorphic rocks (marble, gneiss, mica schist) but also in silica deficient igneous rocks such as siyenites. Name of
the gem was derived from Latin ruber, meaning red. The most valuable rubies have deep red color, known as a pigeon-blood, and seldom are larger than three carats. The finest Mogok
rubies come from Myanmar (Burma). Other areas include Tailand, Cambodia, Sri Lanka, Kenya, etc.

Sapphire
From Latin sapphirus, meaning blue; blue variety of corundum. Sapphires are much more abundant, thus less valuable than rubies. Some of the largest samples exceed 100 carats. The
most highly prized are cornflower-blue stones from Cambodia found in alluvial deposits. Other areas of significant production are Tailand, Sri Lanka, India, and Australia.
Semiprecious gems:

Pearl
One of the oldest known gems. Certain species of saltwater oysters and freshwater clams build concentric layers of aragonite around sand that penetrates their epithelum (mantle).
Pearls may grow flat (blister pearls), irregular (baroque pearls), but most valuable are spherical or drop like pearls. The color of pearls varies with the mollusk species and water
environment. The most valuable are rose Indian pearls. Other colors are cream (Persian Gulf and Japan), white with greenish and bluish shades (Australia), black and reddish-brown
(Mexico), golden-brown (Panama) etc. The value of natural pearls significantly decreased after huge quantities of cultivated pearls invaded the world market.

Amber
Amber is a hardened resin of coniferous trees, usually yellowish brown, but occasionally deep brown to red, green, or blue. Trapped insects, air bubbles, and dust particles may be
found in some specimens. The most abundant amber particles are found along the shores of the Baltic Sea, along the coast of Sicily, and Myanmar (Burma).

Coral
Marine organisms that live in large colonies in shallow, warm, and clear seas. Their skeletal parts precipitate as aragonite and calcite in many different colors and shapes. The most
sought are branch-like corals in red, reddish-rose colors (Mediterranean off the coast of Algeria) and black horn-like corals (Hawaii).