Lesson 4.1 Flashcards
a naturally occurring, inorganic,
homogeneous solid, with a definite
chemical composition, and an ordered
crystalline structure.
Minerals
Physical Properties of Minerals
Color
Streak
Luster
Crystal habit
Cleavage
Fracture
Hardness
Specific gravity
refers to certain wavelengths of light that are reflected by a
mineral and is perceived by the observer.
Color
is the color of the powdered form of a mineral.
Streak
is the appearance of a mineral’s surface and is dependent on
how it reflects light.
Luster
–is the characteristic shape in which a mineral grows
and is a projection of the mineral’s crystal structure.
Crystal habit
is the tendency of some minerals to break along flat
surfaces.
Cleavage
is the pattern in which the mineral breaks aside from its
planes of cleavage.
Fracture
is the resistance of the minerals to scratching.
Hardness
is the ratio of a minerals’ weight to the weight of an
equal volume of water.
Specific gravity
Chemical Properties of Minerals
Solubility
Melting point
refers the ability of a substance to dissolve in a solvent at a
specified temperature.
Solubility
refers to the temperature at which solid turns into liquid.
Melting point
Mineral Groups Based on Chemical Composition
elements
sulfides
halides
oxides and hydroxides
nitates, carbonates, borates
sulfates
chromates,molybdate,tungstates
phosphates, arsenates, vanadates
silicates
Most of the minerals here are composed of only one _.
Having knowledge about elements enables scientists to identify
bonding possibilities and compounds that can be created.
element
Minerals under these group are composed of a metal joined by
a sulfur. Metallic luster is the characteristic that distinguish
them.
Sulfides
These are nonmetal groups which consists of chlorine,
fluorine, bromine, and iodine as their main chemical
constituent.
Halides
These are mineral groups composed of one or more metals
joined with oxygen, water, or hydroxyl (OH–)
Oxides and
hydroxides
It is formed when a metal is combined with carbon, nitrogen
and boron.
Nitrates,
carbonates,
borates
One or more metal is combined with a sulfate compound (SO4)
Sulfates
Chromate, molybdate, or tungstate substituted the place of the
sulfate group. These minerals are usually brightly colored,
brittle and dense.
Chromates,
molybdate,
tungstates
One or more metal is chemically combined with the
phosphates, arsenates, vanadates group.
Phosphates,
arsenates,
vanadates
This is the largest mineral group. Minerals under this group
have different amounts of silicon and oxygen
Silicates
Analysis of the Composition and
Crystal Structure of Minerals
Wet chemical analysis
Spectroscopic techniques
involves
dissolving a mineral in an acid and
analyzing the solution.
Wet chemical analysis
involve quantitative analysis of
mineral components depending
on the light absorbance of the
compounds.
Spectroscopic techniques
most common rock-forming minerals
quartz
feldspar
mica,
pyroxene
amphibole
olivine.
most common rock-forming minerals
quartz
feldspar
mica,
pyroxene
amphibole
olivine.
Self-colored minerals are called
Their color is a diagnostic
property. This means that the color of a mineral is constant and it depends on the
elements that make up their chemical structure.
Examples are malachite (always
green), rhodochrosite (always red) and sulfur (always yellow).
idiochromatic minerals
color is not a reliable diagnostic property since small
impurities may dramatically alter their color. For example, quartz may occur in
different varieties. This includes colorless, milky, smoky, citrine, amethyst, and rose
as shown below
are often weakly-colored or colorless in
their pure state, which allows impurities to pervade them with color
allochromatic minerals
are false-colored minerals. Their colors are due
to light diffraction. In this instance, color may be variable but is an exclusive
properties of the mineral.
pseudochromatic minerals
classifications of mineral color
idiochromatic
allochromatic
pseudochromatic
Minerals appear the same as a pearl or the abalone shell’s interior.
pearly (luster)
It shows similar properties with silk which has fine parallel
threads.
silky (luster)
A mineral has a plain-looking sheen.
dull (luster)
Its characteristics are the same with a resin or chewing gum.
resinous (luster)
Minerals are opaque and looks like Earth or dirt.
earthy (luster)
Minerals are very shiny and brilliant.
adamantine (luster)
occurs if it has the same sheen as a glass.
vitreous or glassy (luster)
A mineral has the same appearance as a polished metal.
metallic (luster)
types of luster
pearly
silky
dull
resionous
earth
adamantine
vitreous or glassy
metallic
Needle-like. Its size is wider than fibrous but thinner than prismatic.
acicular
Its shape is rectangular, but the sides are not necessarily flat.
blocky
Tablet-like. It has flat squares.
tabular
Furry-like. Its sides are thinner than acicular.
fibrous
Its shape is like a knife.
bladed
Plant-like.
dendritic
Pencil-like. Its sides are thicker than acicular.
prismatic
types of crystal habit
acicular
blocky
tabular
fibrous
bladed
dendritic
prismatic
1 cleavage
planes on top of the other
basal
2 cleavage
cleavage at right planes
prismatic
2 cleavage
cleavage not at right angles
non-prismatic
3 cleavage
cleavage at right angles
cubic
3 cleavage
cleavage not at right angles
rhombohedral
4 cleavage
formed 8 faces
octahedral
4 cleavage
formed 12 faces
sphalerite
types of cleavage
basal
prismatic
non prismatic
cubic
rhombohedral
octahedral
sphalerite
Fracture looks like a semi-circular shell.
conchoidal
Fracture appears as jagged points. It has sharp and rough
surface.
jagged
Splintery-fibrous-like fracture
splintery
Rough and irregular fracture. Common in most minerals.
uneven
Types of fracture
conchoidal
jagged
splintery
uneven
relative Mohs scale of hardness
talcm
gypsum
calcite
fluorite
apatite
feldspar
quartz
topaz
corundum
diamond
The
Geologist
Can
Find
An
Ordinary
Quartz
Tourists
Call
Diamond
involves dissolving a mineral in an acid and analyzing
the solution. An acid used is usually hydrochloric acid (5-10%).
If a bubble is evident
after putting drops of the acid, it indicates that carbonate minerals such as calcite and dolomite is present.
wet chemical analysis
uses a controlled flame to separate
the components of a sample and monochromator linked to a detector to
search for wavelengths of light that are absorbed by the sample
Atomic absorption spectroscopy (AAS)
uses argon gas to move
the sample vapor into a chamber under high vacuum where both the sample
and the gas are heated for the elements to give off a characteristic
wavelength of light. This technique is able to trace and identify almost all the
minerals present in the sample.
Inductively coupled plasma (ICP) spectroscopy
uses high voltage electrons toward
a metal target to produce a specific wavelength X-ray beam that hits the
sample. Comparing the sample intensities to that of the standard can be used to calculate the concentration of elements present in the mineral. This
technique will give an analyst a real-time rock analysis. This is more
convenient and efficient than the older technique which takes weeks before
analysis is presented.
X-ray fluorescence (XRF) spectroscopy
is a technique that only applies to
pure amorphous or crystalline substances and is used to study the structure
of the crystals. This process is done by firing an X-ray beam at a finely-ground
sample at different angles. Then reflected or diffracted rays can be used to
compute for the dimensions of the unit cell. This technique is used to obtain
information from unknown crystalline substances particularly most minerals.
X-ray diffraction spectroscopy (XRD)
has a chemical composition of SiO 2
. It
is a glass-like hard substance with white
streaks. It has Mohs hardness of 7 which
makes the _ grains resist scratching of
nail or a pocket knife.
Pure _ is also
known as “rock crystal” that is colorless and
transparent. Trace amounts of impurities
cause colored varieties of _. _ can
occur as amethyst (purple-violet), citrine
(yellow), smoky or cairngorm (brown), morion
(black), rose (pink), sapphire _ (blue), and
milky (semi-translucent white). The grains of
_, in general, are irregular in shape and
exhibits conchoidal fracture.
quartz
has a chemical composition of XAlSi 3O 8
, where X is potassium (K), calcium
(Ca), or sodium (Na). It is quite hard with a Mohs hardness of 6. It is a light-colored
mineral, usually white, but can also exist in lighter shades of red or green. It has a
glassy luster.
In rocks, _ forms rectangular crystals that break along flat
faces.
feldspar
[KAl 3AlSi 3O 10
)(OH) 2
]
occurs as a white, shiny and silvery
mineral. It has a pearly to vitreous
luster, white streak and often sheds
into tiny flakes when scratched.
Muscovite mica
[K 2
(Mg,Fe) 3AlSi 3O 10
(OH,O,F) 2
] is black, dark green, or dark brown,
shiny, and often occurs in small-hexagonal crystals. It has a vitreous luster,
flaky habit and white to gray streak. _ sheets are elastic when bent.
Biotite mica
minerals have a general composition of
XY(Al,Si) 2O 6 where X is calcium (Ca) or magnesium
(Mg) and Y is either magnesium (Mg), iron (Fe), or
aluminum (Al). It occurs as short, stubby and black
to dark-green crystals (although other colors may
occur). It has a glassy luster with streaks of white,
light green, or light brown. It has good cleavage in
two directions (both at almost 90°) and cleavage
surfaces are often hard to see in a regular rock
sample. Augite is the most common mineral of this
group.
Pyroxene
has a general formula of
W 0-1X 2Y 5Z 8O 22
(OH) 2 and has a dark color with a Mohs
hardness ranging from 5 to 6. It is opaque and has
a glassy luster. It occurs as long and slender
crystals. It has good cleavage in two directions
(approximately 60°and 120°) and therefore has a
stair-step appearance under a hand lens.
Hornblende is the most common amphibole.
Amphibole
is a silicate mineral with a general chemical
composition of (Mg,Fe) 2SiO 4
, but calcium,
manganese, and nickel can be substituted for
magnesium and iron. It occurs as small, light green,
glassy crystals. It is commonly used in the
gemstone industry as peridot. It is a glassy looking
and transparent substance that is almost as hard as
quartz. Its sugary or sacharroidal texture and
olive-green color make it distinctive from other
rock-forming minerals.
Olivine
