Transcript Minerals

Aim: What are the characteristics of minerals
and how do we identify them?
I. Minerals
A. 4 Characteristics
1. Naturally occurring
2. solid materials
3. atoms are arranged in an orderly manner
4. inorganic
5. have a definite chemical composition
“NSAID”
B. Rock forming minerals – of the 2400 minerals
on the earth, about a dozen of them are so
abundant that they comprise of more than 90%
of the lithosphere.
1. Lithosphere – outer shell of
the earth consisting of the crust
and uppermost part of mantle.
C. Elements in minerals – mineral’s may be
composed of single elements or compounds of
two or more elements.
1. Most common elements in minerals:
a. Oxygen (O) – since it is the most abundant
element in earth’s crust by both mass (46.6%) and
volume (93.8%).
b. Silicon (Si) – 27.7% by mass and 0.9% by volume.
c. Aluminum (Al)
d. Iron (Fe)
e. Calcium (Ca)
f. Sodium (Na)
g. Potassium (K)
h. Magnesium (Mg)
Silica Tetrahedron
SiO4 – 4 oxygen atoms to every silicon atom
animation
p. 16 ESRT
1.Color – may be used for mineral
identification. Many minerals have the
same color. It is NOT the most reliable
method of identifying a mineral.
Different minerals
with the same
color
2 Different types of quartz –
same mineral, different color.
2. Hardness - the resistance of a mineral to being
scratched. If you scratch two minerals together,
the harder mineral will scratch the softer one.
a. Mohs’ Scale of Hardness - assigns a value
of 1 through 10 to a mineral, with “1” being the
softest value (talc) and “10” being the hardest
value (diamond).
3. Streak – the color of the powder of a mineral when
crushed or scratched across a streak plate (piece of
unglazed porcelain). A mineral’s color may look different
than its streak. Generally, nonmetallic minerals do not
leave a streak.
What are three ways
that we can identify
minerals?
4. Luster – the appearance of light reflected from a
minerals’ surface.
a. Metallic luster – shines like a metal
b. nonmetallic luster – might look glassy, waxy, greasy,
pearly, earthy, or dull.
Nonmetallic
Pyrite (Fools Gold) metallic
5. Cleavage – when a mineral breaks along one or
more smooth surfaces
galena
a. Fracture – when minerals do not break along
flat planes.
Fracture
6. Crystal Structure – a crystal is a regular
shaped solid formed by an ordered pattern of
atoms. Minerals have characteristic crystals.
(Pyrite – calcite)
7. Density
a. Specific gravity – Weight of a mineral
divided by weight of an equal volume of
water.
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