Download Minerals

Minerals:
Building blocks of rocks
Introduction
• What are minerals and how are they different
from rocks?
• What are some of the physical and chemical
properties of minerals?
• What is the most abundant mineral group?
What do all minerals in this group have in
common?
• What are some important nonsilicate minerals?
• When is the term ore used with reference to a
mineral?
Minerals: Building blocks of rocks
Introduction
Definitions
Minerals versus rocks
• rock – an aggregate of minerals
• aggregate – minerals occur together as a
mixture
• each mineral retains its distinctive
properties
• mineral – a naturally occurring inorganic
solid that possesses a definite chemical
structure, which gives it a unique set of
physical properties
Minerals: Building blocks of rocks
Introduction
Definitions
Minerals exhibit the following characteristics:
• naturally occuring
• inorganic
• solid
• definite chemical structure
• unique set of physical properties
Minerals: Building blocks of rocks
Introduction
Properties of minerals
Major properties of minerals:
• crystal form
• hardness
• luster
• cleavage
• color
• fracture
• streak
• specific gravity
Minerals: Building blocks of rocks
Introduction
Properties of minerals
Crystal form
external arrangement of the
orderly internal arrangement of
atoms
Minerals: Building blocks of rocks
Introduction
Properties of minerals
Crystal form – clearly evident only when the
mineral forms without space restrictions
Crystallization
occurs when the
KE of individual
molecules
decreases.
Crystals form as
Most minerals
A supersaturatedthey overcome
form under
intense
solution
readily solvation forces
competition
forms for
crystals
space
Minerals: Building blocks of rocks
Introduction
Properties of minerals
Minerals: Building blocks of rocks
Introduction
Properties of minerals
Luster
appearance or
quality of light
reflected from the
surface
Minerals: Building blocks of rocks
Introduction
Properties of minerals
Luster
• metallic luster
• submetallic luster
• nonmetallic luster
• vitreous
• pearly
• silky
• resinous
• earthy
Minerals: Building blocks of rocks
Introduction
Properties of minerals
Color
Wavelength of visible light bouncing off a surface
Very unreliable diagnostic property due to
impurities
Minerals: Building blocks of rocks
Introduction
Properties of minerals
Streak
• color of mineral powder
• streak plate
• more reliable than color
• metallic (dense, dark streak) vs. nonmetallic
Minerals: Building blocks of rocks
Introduction
Properties of minerals
Minerals: Building blocks of rocks
Introduction
Properties of minerals
Hardness
resistance of a mineral to abrasion
or scratching
use the Mohs scale
Minerals: Building blocks of rocks
Introduction
Properties of minerals
Cleavage
• tendency of a mineral to break along planes of
weak bonding when stressed
• cleavage is described by the number of planes
formed and the angles in which these planes meet
• not all minerals have definite planes of cleavage
Minerals: Building blocks of rocks
Introduction
Properties of minerals
Some examples of cleavage
Minerals: Building blocks of rocks
Introduction
Properties of minerals
Fracture
• minerals that do not exhibit cleavage tend to
fracture when broken
• conchoidal fracture – produces smooth curved
surfaces
• other types of fracture (splinters or fibers)
• most minerals fracture irregularly
Minerals: Building blocks of rocks
Introduction
Properties of minerals
Some examples of fracture
Fibrous fracture –
note formation of
parallel fibers
Conchoidal fracture
– note smooth
curved surfaces
Minerals: Building blocks of rocks
Introduction
Properties of minerals
Specific gravity
compares the weight of a mineral to the weight of
an equivalent volume of water
Minerals: Building blocks of rocks
Introduction
Mineral groups
Mineral groups
Silicates
• most common
• made of oxygen and silicon
• silicon-oxygen tetrahedron is the fundamental
building block
Minerals: Building blocks of rocks
Introduction
Mineral groups
Variants of the silicate structure
• addition of metals to stabilize structure (Fe, Mg,
K, Na, Al, and Ca)
• sharing of oxygen atoms results to a variety of
configurations
• single chains
• double chains
• sheets
Minerals: Building blocks of rocks
Introduction
Mineral groups
Minerals: Building blocks of rocks
Introduction
Mineral groups
Variants of the silicate structure
• the ratio of oxygen to silicon atoms varies among
the different silicate structures
• high or low silicon content based on this ratio
• important in the formation of igneous rocks
• families of minerals
• same structure but with varying amounts of
metals
• olivine, (Mg,Fe)2SiO4
Minerals: Building blocks of rocks
Introduction
Mineral groups
Dark silicate minerals
• ferromagnesian silicates
• contains iron and/or magnesium
• dark color and greater specific gravity
Minerals: Building blocks of rocks
Introduction
Mineral groups
olivine
hornblende
biotite
Minerals: Building blocks of rocks
Introduction
Mineral groups
Light silicate minerals
• nonferromagnesian silicates
• contains Al, K, Ca, and/or Na
• light color and smaller specific gravity
Minerals: Building blocks of rocks
Introduction
Mineral groups
Light silicate minerals
• feldspars – most common light silicates (most
common mineral on Earth)
• orthoclase feldspar – has K ions
• plagioclase feldspar – has Na and Ca
• light color and smaller specific gravity
• quartz – consists entirely of silicon and oxygen
Minerals: Building blocks of rocks
Introduction
Mineral groups
plagioclase feldspar
rose quartz
orthoclase feldspar
Minerals: Building blocks of rocks
Introduction
Mineral groups
Nonsilicate minerals
• carbonate minerals (limestone)
• halite (table salt)
• gypsum (used in plaster, building materials)
• metal ores (Fe, Zn, Pb)
• native elements – free occurring, not in compounds
(Au, Ag, C)
Minerals: Building blocks of rocks
Introduction
Mineral groups
limestone
Minerals: Building blocks of rocks
Introduction
Mineral groups
pink halite
gypsum
Minerals: Building blocks of rocks
Introduction
Mineral groups
malachite
Minerals: Building blocks of rocks
Introduction
Mineral groups
Minerals: Building blocks of rocks
Introduction
Mineral groups
Minerals: Building blocks of rocks