2. Minerals
Typical minerals
Copper – Used in electrical wiring
Gold – Used for jewelry
Talc – Baby powder
Quartz – The main ingredient in glass
A rock can be defined as an aggregate of
two or more minerals, but there are some
exceptions.
3. Earth Mineral
An earth mineral is…
Naturally occurring
Inorganic
Solid
Possesses an orderly internal structure
Has a definite chemical composition
10. Crystal Form
External expression of a mineral’s orderly
internal arrangement of atoms.
Examples
Pyrite – Cubic
Quartz – Hexagonal
11. Luster
The quality of light reflected from the surface
of a mineral.
Examples
Galena - Metallic
Fluorite – Non-metallic
12. Types of Luster
Metallic The mineral is opaque and reflects light
as a metal would.
Submetallic The mineral is opaque and dull. The
mineral is dark
Nonmetallic minerals are described using
modifiers that refer to commonly known
qualities.
Waxy The mineral looks like paraffin or wax.
Vitreous The mineral looks like broken glass.
Resinous The mineral looks like hardened tree
sap.
14. Streak
Color of a mineral in its powdered form.
Examples
Mematite
Oolitic
Color - black
Steak - black
Sepoular
Color - black
Steak - black
15. Hardness
The measure of the resistance of a mineral to
scratching.
Common testing materials
Copper – 3.5
Glass – 5.5
Fingernail – 2.2
17. Cleavage
Tendency of a mineral to break along planes
of bonding
Fracture describes the quality of the
cleavage surface.
fibrous ( dull, silky) fracture
conchoidal (curved, shell-like lines) fracture
irregular (rough, jagged) fracture
18. Cleavage Types
Cubic Cleaves in three directions at 90° to
one another
Rhombohedral Cleaves in three directions
but not at 90° to one another
Octahedral Cleaves in four directions
Dodecahedral Cleaves in six directions
Basal Cleaves in one direction
Prismatic Cleaves in two directions
19. Specific Gravity
Specific Gravity of a mineral is a comparison
or ratio of the weight of the mineral to the
weight of an equal amount of water. The
weight of the equal amount of water is
found by finding the difference between the
weight of the mineral in air and the weight of
the mineral in water.
The most common is 2.5 – 3
20. Others
Taste
Only soluble minerals have a taste, but it is very
important that minerals not be placed in the
mouth or on the tongue.
Feel
Magnetism
Magnetism is the characteristic that allows a
mineral to attract or repel other magnetic
materials.
Reaction to Acid