Yasmin Azeem
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Transcript of Yasmin Azeem
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Yasmin Azeem
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Quartz Crystals
Sulfur
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What is a mineral?
Naturally occurring
Non-organic Characteristic chemical composition
Distinctive physical properties
Crystalline structure
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Mineral A mineral is any naturally-
occurring, homogeneoussolid that has a definite
ch
emical composition anda distinctive internal crystal
structure.
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Most minerals arechemical compounds, a
small number (e.g.,sulfur, copper, gold) are
elements.
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Minerals combine with each
other to form rocks. For example,granite consists of the minerals
feldspar, quartz, mica, and
amphibole in varying ratios.
Rocks are thus distinguished from
minerals by their heterogeneouscomposition.
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Minerals differ from one
another because eachhasa specific chemical
composition and a uniquethree-dimensional
arrangement of atomswithin its structure.
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These differences result in a
variety ofphysical properties,
including the minerals'
appearance, how they break,how well they resist being
scratch
ed, evenh
ow th
eysmell, taste, and feel.
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Mineral properties
Color
Luster
Habit (Shape)
Cleavage & Fracture
Streak
Hardness
Other
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Color Color results from a
minerals chemicalcomposition, impurities
th
at may be present, andflaws or damage in the
internal stru
ctu
re.
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The Many Colors of Fluorite
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Luster The luster of a mineral is the way its
surface reflects light. Most terms
used to describe luster are self-explanatory: metallic, earthy, waxy,
greasy, vitreous (glassy), adamantine
(or brilliant, as in a faceted
diamond).
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Non-metallicMetallic
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Streak The color of a mineral when it is
powdered is called the streak of the
mineral. Streak can be determinedfor any mineral by rubbing the
mineral across the surface of a hard,
unglazed porcelain material called a
streak plate.
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Streak Color for a Few
Common MineralsBlack - GraphiteBlack - Pryite
Black - MagnetiteBlack - ChalcopyriteGray - Galena
Limonite - Yellow-brownHematite - Red-brown
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Streak:
The powdered form of a mineral
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Cleavage & Fracture
Cleavage: planes of weaknessalong whichminerals can break
Fracture: surfaces along whichminerals can break
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Cleavage & Fracture
Best identified on a fracture surface
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Cleavage of
Calcite
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Examples of Cleavage
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Fracture When bonds between atoms are
approximately the same in all
directions within a mineral, breakage
occurs either on irregular surfaces
(splintery or irregular fracture) or
along smooth, curved surfaces
(conchoidal fracture), similar to
those formed when thick pieces of
glass are broken.
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Hardness The hardness of any object
is controlled by th
estrength of bonds between
atoms and is measu
red bythe ease or difficulty with
wh
ich
it can be scratch
ed.
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Diamond is the hardest
mineral, because it can
scratch all others. Talc is
one of the softest; nearly
every other mineral can
scratch it.
iamond is the hardest naturally occurring substance known; it is also
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Hardness:
Based on Mohs scale ofhardness
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Crystal Shape The crystal form for a given
mineral is governed by th
emineral's internal
stru
ctu
re, and may bedistinctive enough to help
identify the mineral.
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Mineral Habit (Shape)
Shape a mineral
takes if grown
unimpeded
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Quartz forms elongated,
six-sided prisms capped
with pyramid-like faces;
galena and halite occur as
cubes; and garnets develop
12- or 24-sided
equidimensional forms.
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Other PropertiesMagnetism - A few
minerals are attracted to amagnet or are themselves
capable of acting asmagnets
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Feel - Some minerals,
notably talc and
graph
ite, feel greasyor slippery when you
rub your fingers overthem
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Taste - Geologists use as many senses as
possible in describing and identifyingminerals. Taste is one of the last tests to
be conducted, because some minerals
are poisonous. Some minerals taste salty-most notably halite (salt). Sylvite, a
mineral similar in all other properties to
halite, tastes bitter. NEVER TASTE AMINERAL UNLESS INSTRUCTED TO!
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Reaction with Dilute
Hydrochloric Acid-Th
is isactually a chemical property
rather than a physical attribute of
a mineral. Minerals containingthe carbonate anion (C03)
2-
effervesce ("fizz") wh
en a drop ofdilute hydrochloric acid is placed
on them.
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