Minerals

Minerals

Minerals are naturally-occurring solids that have a crystal structure, are inorganic,  and have a definite chemical composition.
 
Naturally-occurring- not man-made
Solid- keeps its shape
Crystal-repeating pattern of shapes in the particles
Inorganic- not made of living things
Definite chemical composition- contains elements in definite proportions
 
Crystals
 
uHave a repeating pattern of particles
uHave flat sides (faces)
uHave sharp edges and corners
 

 

Quartz Often Exhibits Good Crystal Form.
 
Definite Composition
 
Element:
Substance composed of one kind of atom. Atoms are
the smallest particles of an element. Elements are the basic building blocks of minerals.
 
Compound:
Two or more elements combined.
 
What are minerals and what are their characteristics?
 
Properties of Minerals
 
Hardness
 
u Hardness is a measure of the resistance of a mineral to being scratched.
 
u Mohs scale consists of 10 minerals arranged from 10 (hardest) to 1 (softest).
 
Mohs Scale of Hardness

Mohs Hardness Scale

Number - Description - Example Mineral

1 - rubs off on fingers - talc

2 - can be scratched by fingernail - gypsum

3 - can be scratched by a copper penny - calcite

4 - can be scratched by a steel nail - fluorite

5 - can be scratched by a steel nail - apatite

6 - scratches glass - feldspar

7 - scratches steel or glass - quartz

8 - scratches quartz - topaz

9 - scratches topaz - corundum

10 - scratches all materials - diamond

 

Color
 
u Small amounts of different elements can give the same mineral different colors.
 
Streak
 
u Streak is the color of a mineral in its powdered form.
 
Luster
 
u Luster is used to describe how light is reflected from the surface of a mineral.
 
Pyrite (Fool’s Gold) Displays
Metallic Luster.
 

 
Density
 
u Density is mass per volume.
 
Crystal Systems

uu The pattern of how the crystals are arranged.

uu There are six different crystal systems

 
Cleavage
 
u Cleavage is the tendency of a mineral to cleave, or break, along flat, even surfaces.
 
Mica Has Cleavage in One Direction

Fracture
 
u Minerals that do not show cleavage when broken are said to fracture.
 
u Fracture—the uneven breakage of a mineral
 
Special properties
 
u Magnetic
u Fluorescent
u Electrical 
u Radioactive
 
 
How Minerals Form
 
1. Crystallization from magma
  • As magma cools inside the crust (or as lava cools on the surface), minerals form.
  • Fast cooling: smaller crystals
  • Slower cooling: larger crystals
 
Minerals Formed as a Result of Crystallization of Magma

2. Crystallization of materials dissolved in water 
  • Magma heats water beneath the surface.
  • This water is solution containing many elements. As hot water from beneath the surface cools, the elements crystalize into minerals.
3. Crystallization from evaporation
  • As oceans and seas have evaporated, they have left deposits of crystals.








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