Transcript Chapter 5.1: Minerals

Minerals
5.2 Composition and Structure
of Minerals
What is a mineral?
• A mineral has the following characteristics:
– It occurs naturally.
– It is a solid.
– It has a definite chemical composition.
– Its atoms are arranged in an orderly pattern.
– It is inorganic (never alive or produced by
something that was alive.)
Minerals
Name
Symbol
• There are about 4000 Oxygen
O
known minerals
Silicon Si
– Examples) gold,
Aluminum Al
quartz, halite (salt),
diamond
Iron
Fe
• 8 elements make up
Calcium Ca
98.5% of the crust’s
Sodium Na
total mass.
Potassium
K
• Most minerals are
Magnesium
Mg
compounds.
Other -
%
46.6
27.7
8.1
5.0
3.6
2.8
2.6
2.1
1.5
Minerals Through the Magma
Process
• Many minerals form out of molten rock.
• In magma, atoms or ions can move freely.
• As magma cools the atoms, molecules and ions
move closer together and form chemical bonds
that create compounds.
• Many different minerals can form from the same
magma mass.
• The types of minerals that form depend on:
– The types of elements present in the magma
– The rate at which the magma cools determines the
crystal size.
Minerals Through the Pressure
Process
• When a rock is subjected to high
temperature and pressure, the minerals
begin to break down chemically.
• The temperature and pressure becomes
great enough to change the mineral in a
solid state.
• The free atoms, ions, and molecules
recombine forming new minerals.
Structure of Minerals
• Minerals form crystals.
– A regular geometric solid with smooth
surfaces called crystal faces.
– Contain a regularly, orderly arrangement of
atoms.
• Although there are thousands of different
minerals, there are only 6 basic different
shapes of crystals.
Six Crystal Systems
Silicates
• Silicon and oxygen are the two most abundant
elements in the Earth’s crust.
• Most minerals (90%) contain these two elements
and are called silicates.
• A silicate may contain one or more metallic
elements.
• The basic building block of a silicate is the
silicate tetrahedron.
– Consists of 4 oxygen atoms around a silica atom.
– Named for its shape.
Silica Tetrahedron