Atoms

Atoms – basic building blocks for all earth
materials; consist of 3 basic components:
protons, neutrons, electrons
Atoms combine to form
Elements

Elements – fundamental component that
can not be broken down into other
substances by ordinary chemical
processes

Elements combine to form minerals
General Facts About Minerals
2,000 + minerals have been identified
A few are “native elements” -- made of
only one element, such as sulfur, gold.
copper, and graphite (carbon)
 Most are compounds, especially the
silicate group (Si, O).
 Other important groups are oxides,
carbonates, and sulfides.

MINERALS
NATIVE ELEMENTS
Gold (Au)
Silver (Ag)
Platinum (Pt)
Diamond (C)
Graphite (C)
Sulfur (S)
Copper (Cu)
Gold
Copper
Silver
Mineral Criteria
1.
 2.
 3.
 4.

Crystalline solid
Naturally occurring
Have a definite chemical composition
Inorganic
Minerals are identified by their
Physical Properties
Crystal Form
 Color
 Streak
 Luster – metallic, non-metallic
 Hardness – Moh’s Hardness Scale (1-10)
 Cleavage
 Fracture
 Specific Gravity
 Others

A mineral’s physical properties
are controlled by its internal
arrangement of atoms
regularly repeating, orderly pattern
The most common crystalline
structure

Silica-oxygen tetrahedron – basic
building block for silicate minerals
Silica tetrahedron combine
several different ways
Five major types of
silicate minerals
based on their
structure
A) Isolated tetrahedron
B) Single chain
C) Double chains
D) Sheet silicates
E) 3-D framework
silicates
Minerals can have the same chemical composition
(Carbon) but different physical properties because
of their crystal structure
Diamond
Graphite
COLOR
Color is not usually a definitive property of
a mineral.
 Some minerals have characteristics colors
 Others vary due to chemical differences or
impurities (atoms mixed inside the main
elements)
 However most minerals have a variety of
colors.

Some Colors of Quartz
STREAK

For opaque minerals, if you rub the
sample across a streak plate, it will leave a
colored powder. This streak is distinctive
for minerals and is used to identify
minerals.
Varieties of Hematite – all same color streak
HARDNESS – Mineral’s resistance to
scratching. Minerals with higher numbers
will scratch minerals below
LUSTER

Describes how light reflects off the surface

Categories: Metallic or non-metallic
Metallic does not mean shiny

Non-metallic: vitreous or glassy; silky;
resinous; pearly; greasy; waxy, dull; earthy
Examples of metallic luster
More Examples of Metallic Luster
Pyrite (FeS2)
Galena (PbS)
PYRITE
GALENA
Example of non-metallic luster

Vitreous--quartz
Example of non-metallic luster

Silky--example plagioclase feldspar
Non-metallic and metallic luster –
earthy hematite – metallic hematite
Cleavage and Fracture
Some minerals split along flat surfaces
when struck hard--this is called mineral
cleavage
 Other minerals break unevenly along
rough or curved surfaces--this is called
fracture
 A few minerals have both cleavage and
fracture ( mica )

Cleavage
Halite (NaCl)
Fluorite (CaF2)
HALITE
FLUORITE
Cleavage
MUSCOVITE
BIOTITE
Rose Quartz – Conchoidal Fracture
Conchoidal Fracture - Quartz
Obsidian
DENSITY / SPECIFIC GRAVITY

This is the ratio of the density of the
mineral to the density of water.

Weight Air/(Weight Air-Weight in water) =
specific gravity
Acid Test for Carbonates

Special Characteristics:
Carbonates react with dilute HCl and other
acids by fizzing or bubbling (releasing
CO2 gas)
MINERALS
NONSILICATE MINERALS
CARBONATES
Carbonate ion (CO32-) is prominent in minerals.
Has -2 charge.
Combines readily with positive ions.
Bonds generally weak.
Minerals are soft (3-4).
Minerals are soluble in acidic water.
Leads to cave development.
Calcite (CaCO3)
Dolomite (CaMg(CO3)2)
DOLOMITE
CALCITE
Less than a dozen are common in
most rocks

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Quartz
Feldspar (group)
Muscovite (silver white mica)
Biotite (black mica)
Calcite
Pyroxene
Olivine
Amphibole (group)
Magnetite, limonite, and other iron oxides
Pyrite
Common uses include:




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Aluminum--packaging, transport, building
Beryllium--gemstones, fluorescent lights
Copper--electric cables, wires, switches
Feldspar--glass and ceramics
Iron--buildings, automobiles, magnets
Calcite--toothpaste, construction