www.middleschoolscience.comwww.middleschoolscience.com 2009
http://www.gc.maricopa.edu/earthsci/imagearchive/index.htm Minerals
and Rocks
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S olid Cannot be a liquid or a gas N aturally Occurring Found
in nature, not man-made I norganic Is not alive and never was,
non-living F ixed composition Has a chemical formula, most are
formed from compounds of two or more elements, some minerals
consist of one element ex. Au C rystal Form A definite structure in
which atoms are arranged
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Is it non-living material? Is it a solid? Is it formed in
nature? Does it have a crystalline structure?
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Gold
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Fossil
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Topaz
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Bones
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Granite
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Quartz
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Pearls
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Talc
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Icebergs
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Diamond
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Coal
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Rock Salt
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Minerals a) Gold b) Topaz c) Quartz d) Talc e) Iceberg* f)
Diamonds Non-Minerals a) Wood - once living b) Fossils once living
c) Bone - living material d) Granite - intrusive igneous rock e)
Pearls made by oysters f) Coal - Sedimentary rock g) Rock Salt
Sedimentary rock According to IMA ice is listed as a
mineralIMA
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A mineral is a naturally formed, inorganic solid that has a
definite crystalline structure.
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Mineral Identification Basics PHYSICAL PROPERTIES HARDNESS
HARDNESS is defined as the resistance a mineral has to being
scratched - its scratchability. Hardness tests are done by
scratching one mineral against another. The mineral that is
scratched is softer than the other. Pyrite Crystals Hardness of
6.5
Mineral Identification Basics PHYSICAL PROPERTIES CLEAVAGE
CLEAVAGE is the property of a mineral that allows it to break
repeatedly along smooth, flat surfaces. These GALENA cleavage
fragments were produced when the crystal was hit with a hammer.
Note the consistency of the 90 o angles along the edges. These are
FLUORITE cleavage fragments.
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Mineral Identification Basics PHYSICAL PROPERTIES CLEAVAGE
Within this crystalline pattern it is easy to see how atoms will
separate to produce cleavage with cubic (90 o ) angles.
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Mineral Identification Basics PHYSICAL PROPERTIES CLEAVAGE
These pictures show different cleavage angles and the quality of
cleavage. Fluorite has cleavage in four directions A thin sheet of
Muscovite seen on edge. Mica has perfect cleavage in ONE
direction.
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Mineral Identification Basics PHYSICAL PROPERTIES CLEAVAGE
Common salt (the mineral HALITE) has very good cleavage in 3
directions. These 3 directions of cleavage are mutually
perpendicular resulting in cubic cleavage.
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Mineral Identification Basics PHYSICAL PROPERTIES STREAK STREAK
is defined as the color of the mineral in powder form. Hematite on
Streak Plate Streak is normally obtained by rubbing a mineral
across a streak plate. This is a piece of unglazed porcelain. The
streak plate has a hardness of around 7 and rough texture that
allows the minerals to be abraded to a powder. This powder is the
streak. Hematite has a reddish brown streak.
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Mineral Identification Basics PHYSICAL PROPERTIES LUSTER LUSTER
is defined as the quality of reflected light. Minerals have been
grossly separated into either METALLIC or NON- METALLIC lusters.
Following are some examples: Native Silver has a Metallic
Luster
Mineral Identification Basics NON METALLIC NON METALLIC LUSTER
Miscellaneous Lusters Asbestos - SilkyApophyllite - Pearly Limonite
- Dull or Earthy Sphalerite - Resinous Graphite has a greasy or
submetallic luster and easily marks paper.
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Mineral Identification Basics PHYSICAL PROPERTIES COLOR The
COLOR of a mineral is usually the first thing that a person notices
when observing a mineral. However, it is normally NOT the best
physical property to begin the mineral identification process.
Following are some examples of color variation within mineral
species followed by minerals that have a distinctive color: Various
colors of CALCITE.
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Clear - Without Impurities Mineral Identification Basics
PHYSICAL PROPERTIES COLOR Various colors of Quartz. Hematite
Inclusions Chlorite inclusions Amethyst Ionic Iron
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Mineral Identification Basics INDICATIVE COLOR Turquoise Sulfur
Malachite Rhodochrosite Azurite
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Mineral Identification Basics PHYSICAL PROPERTIES SPECIFIC
GRAVITY The SPECIFIC GRAVITY of a mineral is a measure of the
minerals density. It is related to the types of elements that make
up the mineral and how they are packed into the minerals atomic
structure. Gold in Quartz Gold has a Specific Gravity of 19.2. It
is 19.2 times the weight of an equal volume of water. Water has a
Specific Gravity of 1.
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Mineral Identification Basics PHYSICAL PROPERTIES SPECIFIC
GRAVITY The SPECIFIC GRAVITY of a mineral is determined by weighing
the specimen in air and then weighing it in water. It is the ratio
of an objects density to the density of water. (Weight in air) -
(Weight in water ) Weight in air Specific Gravity =
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Mineral Identification Basics PHYSICAL PROPERTIES TASTE IT IS
NOT RECOMMENDED THAT A TASTE TEST BE PERFORMED ON MINERALS AS A
STANDARD PROCESS. SOME MINERALS ARE TOXIC. However, the mineral
HALITE is common salt and has a unique taste. Halite cubes from
Trona, CA
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Mineral Identification Basics PHYSICAL PROPERTIES MAGNETISM
MAGNETISM is the ability of a mineral to be attracted by a magnet.
This most commonly is associated with minerals rich in iron,
usually magnetite. This is a piece of MAGNETITE with a magnet
adhering to it. Magnetite is strongly magnetic in that a magnet
will easily be attracted to it.
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Mineral Identification Basics PHYSICAL PROPERTIES DIAPHANEITY
The manner in which minerals transmit light is called DIAPHANEITY
and is expressed by these terms: TRANSPARENT: A mineral is
considered to be transparent if the outline of an object viewed
through it is distinct. TRANSLUCENT: A mineral is considered to be
translucent if it transmits light but no objects can be seen
through it. OPAQUE: A mineral is considered to be opaque if, even
on its thinnest edges, no light is transmitted. Quartz with
Spessartine Garnets
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Mineral Identification Basics PHYSICAL PROPERTIES DIAPHANEITY
TRANSPARENT: A mineral is considered to be transparent if the
outline of an object viewed through it is distinct. Topaz from
Topaz Mountain, Utah
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Mineral Identification Basics PHYSICAL PROPERTIES DIAPHANEITY
Sylvite from Salton Sea, California TRANSLUCENT: A mineral is
considered to be translucent if it transmits light but no objects
can be seen through it. Backlit Apophyllite Crystals
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Mineral Identification Basics PHYSICAL PROPERTIES DIAPHANEITY
Schorl - The black variety of Tourmaline OPAQUE: A mineral is
considered to be opaque if, even on its thinnest edges, no light is
transmitted.
