minerals. minerals must have four characteristics: ▪ it must be inorganic—not made of or by...
TRANSCRIPT
MINERALS
What is a Mineral?
Minerals must have four characteristics:▪ it must be inorganic—not made of or by
living things;▪ it must occur naturally—it cannot be man-
made;▪ it must be a crystalline solid;▪ it must have a consistent chemical
composition.
Types of Minerals
10 are so common that they make up 90% of Earth’s crust. quartz, orthoclase, plagioclase, muscovite,
biotite, calcite, dolomite, halite, gypsum, and ferromagnesian minerals.
Two main groups: silicate minerals nonsilicate minerals
Silicate Minerals
Contain silicon and oxygen, and possibly one or more metals
Common silicate minerals quartz, feldspars, micas ,and ferromagnesian
minerals, such as amphiboles, pyroxenes, and olivines.
Make up 96% of Earth’s crust. Quartz and feldspar alone make up more than
50% of the crust.
Nonsilicate Minerals
No silicon and oxygen compounds
Make up about 4% of Earth’s crust.
Six major groups based on their chemical compositions carbonates, halides, native elements,
oxides, sulfates, and sulfides.
Mineral Structure
Each type of mineral is characterized by a specific geometric arrangement of atoms, or its crystalline structure.
A crystal is a solid whose atoms, ions, or molecules are arranged in a regular, repeating pattern
Silicate Structure
Silicon-Oxygen Tetrahedron- basic unit of the structure of silicate minerals. Si+4 and 4 O-2
Ex: Olivine
Ex: Beryl and tourmaline
Silicate Structure
Ex: Pyroxenes
Ex: Amphiboles
Silicate Structure
Ex: Biotite and muscovite
Silicate Structure
Ex: Quartz and feldspar
Nonsilicate Structure
Diverse chemical compositions = vast variety of crystalline structures.
Common nonsilicate mineral structures: cubes, hexagonal prisms, and irregular
masses.
Mineral Identification
Mineralogist- a person who examines, analyzes, and classifies minerals
Chemical composition and crystalline structure determine a minerals properties
Many of these properties can be used to identify a mineral sample.
Mineral Properties
ColorEasily observed but unreliable
for mineral identification.Can be affected by impurities or
weathering.
StreakColor of a mineral in powdered
formStreak is more reliable than color
for the identification of minerals.
Mineral Properties
Luster
The way a mineral reflects light
Metallic luster- reflects light like polished
metals.
Nonmetallic luster- duller appearance
glassy, waxy, pearly, brilliant, and earthy.
Mineral Properties
Mineral Properties
Cleavage- tendency of a mineral to split along specific planes to form smooth, flat surfaces
Cleavage and Fracture
Mineral Properties
Types of Cleavage Muscovite Halite
Feldspar
Mineral Properties
Fracture- breaks along curved or irregular surfaces Uneven or irregular
fractures Splintery or fibrous
fractures Conchoidal
fractures
Cleavage and Fracture
Mineral Properties
Hardness
Ability of minerals to resist scratching.
Does NOT mean “resistance to cleavage or fracture.”
Determined by comparing to minerals
Mohs hardness scale the standard scale for the
hardness of minerals.
The strength of the bonds between the atoms of a
mineral determines its hardness.
Mineral Properties
Mineral Properties
Crystal Shape
Certain minerals always have the same general shape because the atoms that form the mineral’s crystals always combine in the same geometric pattern.
The six basic crystal systems: isometric or cubic, orthorhombic, tetragonal,
hexagonal, monoclinic, and triclinic
Mineral Properties
Mineral Properties
Density
density the ratio of the mass of a substance to the volume of a substance
The density of a mineral depends on the kinds of atoms in the mineral and on how closely the atoms are packed.
density = mass volume
Special Properties of Minerals
The ability to glow under UV light is called fluorescence.
The property of some minerals to glow after the ultraviolet light is turned off is called phosphorescence.
Fluorescence and Phosphorescence
Chatoyancy and Asterism
Light is reflected causing a silky appearance that is called chatoyancy Tiger’s Eye
A similar light reflecting effect called asterism is when a six-sided star appears Star Sapphire
Special Properties of Minerals
Double Refraction
Producing a double image of objects viewed through the mineral.
Special Properties of Minerals
MagnetismAre attracted to
magnets or may be magnetic themselves.
In general, nonsilicate minerals that contain iron are more likely to be magnetic than silicate minerals are.
Special Properties of Minerals
Radioactivity
The property known as radioactivity results as unstable nuclei decay over time into stable nuclei by releasing particles and energy.
A Geiger counter is used to detect the released particles and, thus, to identify minerals that are radioactive.
Special Properties of Minerals
Value of Minerals