ch03 Atoms, Elements, Minerals, Rocks Earths Building Materials.ppt

Chapter 3: Atoms, Elements, Minerals, Rocks: Earth’s Building Materials
Mineral
Naturally formed, anic, solid material with a specific position and a characteristic crystalline structure.
Rock
Naturally formed, coherent mass of one or more minerals, sometimes anic debris.
Introduction : What Is A Mineral?
Key Characteristics of Minerals
Minerals have two key characteristics.
Composition:
The chemical elements pose a mineral, and their proportions.
Crystal structure:
anized way in which the atoms of the elements are packed together in a mineral.
Composition of Minerals
A few minerals posed of a single element (diamond, graphite, gold, copper, and sulfur).
Most minerals pounds, containing more than one element.
Chemical elements are the most fundamental substances into which matter can be separated by chemical means.
Crystal Structure of Minerals
The atoms in most solids anized in regular, geometric patterns, called the crystal structure.
Solids that have a crystal structure are said to be crystalline.
Ice in a glacier meets the definition of a mineral.
Solids that lack crystal structures are amorphous.
glass and amber.
Crystal Form
Crystal: any solid body that grows with planar surfaces.
The interfacial angle in any crystalline structure remains constant.
Iregular Growth of Quartz grains
Fibers of Chrysotile Asbestos
Growth Habit and Polymorphism
Growth habit:
The characteristic crystal form of each mineral.
Polymorphism:
Some elements pounds form two or more different minerals:
C Graphite, Diamond
CaCO3 Calcite, Aragonite
FeS2 Pyrite, Marcasite 白铁矿
SiO2 Quartz, Cristobalite 方英石
Cleavage
Cleavage is the tendency to break in preferred directions along bright, reflective planar surfaces.
A cleavage surface is a breakage surface, whereas a crystal face is a growth surface.
The planar directions along which cleavage occurs are governed by the crystal structure.
They are planes along which the bonding between atoms is relatively weak.