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http://www.mii.org/
What is a mineral?

A mineral:
 is naturally-occurring.
○ not manmade
 is an inorganic solid.
○ It has never been a part of a living thing.
 has a definite chemical composition.
○ It has specific elements that make up its compounds.
○ NaCl is always halite, which is table salt. It is a
compound of sodium and chlorine.
 has an orderly arrangement of atoms.
○ Minerals are made of crystals, which have specific
shapes.
○ All minerals are solids.
Atom Patterns in Minerals

Minerals are crystalline solids.

The atoms of minerals are arranged in
patterns that repeat.
The Structure of Minerals
A crystal is a solid in which the atoms are
arranged in orderly, repeating patterns.
 A crystal system is a group of crystals that
has

 a similar atomic arrangement.
 a similar overall crystal shape.

http://www.minerals.net/MineralMain.aspx
Crystal Systems of Minerals
Hexagonal
 Six-sided crystals
 Examples:

 Emeralds
 Aquamarine
Crystal Systems of Minerals
Tetragonal
 Example:

 Zircon
Cassiterite from
Madagascar
Apophyllite
Crystal Systems of Minerals
Cubic
 Examples:

 Halite, which is
common table
salt.
 Fluorite, which is
an additive in
toothpaste used
to prevent
cavities.
Crystal Systems of Minerals
Orthorhombic
 Example:

 Sulfur
 Topaz
Crystal Systems of Minerals
Monoclinic
 Example:

 Selenite
gypsum
Crystal Systems of Minerals
Triclinic
 Very little
symmetry
 Example:
amethyst

More on crystals . . .

There are about 4000
different types of minerals
on Earth.

Crystals that develop in a
tight space will have small,
barely visible crystal
shapes.

Crystals that develop in
open spaces will have
more room to grow larger,
visible crystal shapes.
Crystals from Magma
Hot, melted rock material that is under
Earth’s crust is called magma.
 Magma is loaded with compounds that can
form minerals.
 If magma cools slowly, the crystals have
more time to form and can grow quite large.
 If magma cools quickly, smaller crystals form
and individual crystals can’t be seen.

Crystals from Solution

Crystals can form when minerals dissolve in
water and the water evaporates.

http://news.nationalgeographic.com/news/2007/04/photogalleries/gi
ant-crystals-cave/

Death Valley Salt fields were formed from
halite that came out of solution as water
evaporated.
Devil’s Golf Course, Death
Valley, California
Mineral Compositions & Groups

Ninety-two elements occur naturally in Earth’s
crust.

Most of Earth’s crust is composed of only 8 of
these elements.

Silicates are minerals that contain a
compound of silicon and oxygen bonded
together, usually with another element.
 Silicon and oxygen are the two most abundant
elements in Earth’s crust.