Rocks And Minerals
According to Webster’s Dictionary, the definition of a mineral is an
inorganic
substance. Citrine is one of the most popular minerals. It is a
variety of
quartz. Citrine is a yellowish-orange mineral. Citrine is a very
popular
gemstone because it is very affordable and very pretty. Along with
topaz,
citrine is the birthstone for the month of November and the
anniversary gemstone
for the 17th year of marriage (www.jewelrymall.com).
Citrine is also considered
a symbol of hope, youth, health, and fidelity
(www.houseofonyx.com). In ancient
times, citrine was carried as a protection
against snake venom and evil thoughts
(www.jewelers.net). Other names for
citrine are Imperial Topaz, Oriental Topaz,
and Precious Topaz. Chemical
Formula A chemical formula is what elements make up
the mineral (Feather
& Snyder, 1999). These elements can be found on the
periodic table. The
chemical formula of citrine is SiO2, which is silicon and
oxygen
(www.galleries.com). Silicate or Non-silicate According to
Webster’s
Dictionary, a silicate mineral is a combination of silicon,
oxygen, and one or
more minerals. Because citrine is made up of silicon and
oxygen, it is a
silicate mineral. Physical Properties The properties you can
observe without
changing a substance into a new substance are physical
properties (Feather &
Snyder, 1999). The five main physical
properties in minerals are hardness,
cleavage, fracture, streak and luster.
Hardness Hardness is a measure of how
easily a mineral can be scratched.
Hardness is usually measured on Mohs hardness
scale. The scale is measured
from one to ten, with one being the softest and 10
being the hardness
(Feather & Snyder, 1999). All kinds of quartz have a
hardness of seven.
Because citrine is in the quartz family, it has a hardness of
seven
(www.galleries.com). Cleavage & Fracture Minerals that break along
smooth
flat surfaces have cleavage. Cleavage is determined by the arrangement
of
mineral’s atoms (Feather & Snyder, 1999). Citrine has no
cleavage,
therefore it has fracture. Minerals that break with rough or jagged
edges have
fracture. Citrine has fracture because it has no cleavage (Feather
& Snyder,
1999). Streak The color of a mineral when it is broken up
and powdered is called
streak (Feather & Snyder, 1999). The streak of
citrine is white. Luster
Luster describes how light is reflected from a
mineral’s surface (Feather
& Snyder, 1999). The luster of citrine is
vitreous, or closely resembles
glass (www.minerals.net). Location Citrine is
found in most places but most
miners and manufacturers go to Brazil to find
it because of the quality and
availability there (www.jewelers.net). Uses
Citrine is mostly used for jewelry
but is also found in oscillators and
timepieces for radios (www.jewelryblvd.com).
Citrine is also used a lot
as a substitute for yellow sapphire and yellow
diamond. Minerals are found in
many kinds of rocks. In this next section, you
will learn how minerals make
up rocks, and how rocks are formed. A rock is a
mixture of minerals,
mineraloids, glass, or organic matter (Feather &
Snyder, 1999). Most
people know what a rock is but they don’t know how it
forms. The process of
how rocks form is called the rock cycle. In this report,
you will learn about
the stages in the rock cycle and the three different types
of rock in the
rock cycle. Background James Hutton came up with the rock cycle.
Hutton
is known as the eminent 18th century farmer and founder of modern
geoscience
(www.science.ubc.ca). Scientists all over the world are still
using
Hutton’s rock cycle today. Igneous Rocks Igneous rocks are
sometimes referred
as fire rocks. They form under ground or above ground
(Feather & Snyder,
1999). All igneous rocks are formed in the process
of volcano formation (www.windows.umich.edu).
Igneous rocks come in two
forms, intrusive and extrusive. Intrusive Rocks Rocks
that form below the
earth’s surface are called intrusive rocks (Feather &
Snyder, 1999).
Intrusive rocks form when magma gets trapped in small pockets
below the
earth’s surface. As these pockets of magma cool, the magma becomes
igneous
rocks. (www.fi.edu). Extrusive Rocks Extrusive rocks are formed when
lava
from volcanoes cool on or near the earth’s surface (Feather &
Snyder,
1999). The lava cools because it is exposed to air and moisture.
The air and
moisture cause the rock to harden. The harden magma becomes rocks
called
extrusive rocks (Feather & Snyder, 1999). An example of an
extrusive rock is
rhyolite. Rhyolite An example of a fine-grained, extrusive
igneous rock is
rhyolite. Rhyolite is an igneous rock because it forms from
volcano eruptions.
Rhyolite can look very different depending on how it
erupts (www.volcanoes.usgs.edu).
Rhyolite can be made up of many
different colors ranging from dark gray to pink
(www.infoplease.com). Special
pieces of rhyolite will show a spider webbing
design. Mineral make-up
Rhyolite is very closely related to granite. The
difference is rhyolite has
much finer crystals. These crystals are so small that
they cannot be seen by
the naked eye. Rhyolite very rapidly which gives it a
glassy appearance. The
minerals that make up rhyolite are quartz, feldspar,
mica, and hornblende.
All of this information is according to
www.volcano.nodak.edu. Location
Rhyolite is found all over the world where there
are volcanic mountains
(www.britannica.com). Certain colors of rhyolite are
found in certain places,
though. For example, certain kinds of red rhyolite are
only found in
California and parts of Nevada. This information is according
to
www.encarta.msn.com. Uses Rhyolite has no uses because it is a volcanic
rock.
Some rock collectors think rhyolite is valuable rock, though. An
igneous rock is
just one of three types of rocks. Another type of rock is a
sedimentary rock.
Sediments Sediments are loose material such as rock
fragments, mineral grains,
and bits of plant and animal remains that have
been moved by wind, water, ice,
or gravity. These sediments form a rock
called a sedimentary rock. Sedimentary
Rock Rocks that form when
sediments become pressed or cemented together are
called sedimentary rocks
(Feather & Snyder, 1999). Sedimentary rocks cover
about 75% of the
earth’s surface. Sedimentary rocks are usually classified by
two kinds,
detrial or chemical. Detrial Sedimentary Rocks Rocks that are made
from
broken fragments or other rocks are called detrial rocks (Feather
&
Snyder, 1999). These broken fragments compact or cement together
like all
sedimentary rocks. Detrial rocks are often referred to as clastic
rocks. Clastic
Detrial sedimentary rocks are often referred to as clastic
rocks because of
their texture. The word clastic comes from the Greek word
meaning "broken"
(Feather & Snyder, 1999). Clastic rocks are from solid
grain unlike chemical
sedimentary rocks (www.oswego.edu). Examples of clastic
rocks are sandstone and
shale. Chemical Sedimentary Rocks Rocks that form
from minerals precipitating
out of water are called chemical sedimentary
rocks. The deposits of minerals
that remain after evaporation harden, and
form chemical sedimentary rocks. An
example of a chemical sedimentary rock is
limestone. Limestone Limestone is a
fine-grained, chemical sedimentary rock.
It is a sedimentary rock because it
forms from sediments being pressed or
cemented together (Feather & Snyder,
1999). Most limestone is gray
but all colors of limestone from white to black
have been found
(www.artistictile.net). It commonly contains fossils such as
shells or other
animal remains. In some cases, the fossils make up most of the
rock
(www.em.gov.bc.ca). Mineral make-up Limestone is mostly made up of
the
mineral calcite. The other minerals in limestone can differ greatly
because it
is found in a lot of environments. Examples of these other
minerals are dolomite
and aragonite. Location Limestone is found all over the
world but the most
common form of limestone is found in marine environments.
Uses Limestone makes
an excellent building stone because it can be carved
easily. It can be cut any
way without splitting. Limestone is especially good
for foundations and walls
where a high polish is not needed. Limestone is
also used in concrete. Some
factories use limestone to clean waste gases and
water before releasing them
into the environment. I have completed telling
you about igneous and sedimentary
rocks. Next, I will tell you about the 3rd
and final type of rock, metamorphic
rocks. Metamorphic Rocks Metamorphic
rocks are formed by action of pressure,
temperature, and fluids. When rocks
are deeply buried into the earth, they can
deform. New minerals crystallize
on them to form metamorphic rocks (www.marshallnet.com).
The two kinds of
metamorphic rocks are foliated and non-foliated. Foliated Rocks
When
mineral grains flatten and line up in parallel bands, it is called a
foliated
rock (Feather & Snyder, 1999). Foliated rocks look like
stepping-stones
or stair steps. They are arranged into layers when they are
exposed to heat
and pressure unlike non-foliated rocks. Non-foliated rocks
Metamorphic
rocks where no banding occurs are called non-foliated rocks.
Minerals
inside the rocks change, grow, and rearrange, but they don’t band
together
like foliated rocks (Feather & Snyder, 1999). One example of
a
non-foliated rock is marble. Marble Marble is a non-foliated metamorphic
rock.
Marble is a rock formed by the metamorphism of limestone. Marble
can be a
variety of colors depending on various impurities. Marble is
always
distinguished by being softer than glass. (www.calvin.edu). Mineral
make-up
Marble is primarily composed of the mineral calcite
(www.minerals.net). Some
marble has variations of minerals. The variations
give marble a wide variety of
colors (www.artistictile.net). Location Marble
is found in many countries,
including Belgium, France, Greece, India, Italy,
Spain, and the United Kingdom.
Some South American nations also have some
marble. In the United States, Georgia
produces the most marble. Other marble
producing states include Alabama,
Colorado, Montana, Tennessee, Texas,
and Vermont (www.artistictile.net). Uses
Marble has been highly valued
for its beauty, strength, and resistance to fire
and erosion. The ancient
Greeks used marble in many buildings and statues and it
is still being used
today in floors and other parts of buildings. Smaller pieces
of marble are
crushed and used as abrasives in soaps. Crushed marble is also
used in paving
roads and in roofing materials (www.minerals.net). That concludes
the three
types of rocks. Now you will learn about the process of the rock
cycle. The
process of the rock cycle Molten rock material solidifies at depth or
at the
earth’s surface to form igneous rocks. Uplift and exposure of rocks at
the
earth’s surface destabilizes the mineral structures. The minerals break
down
into smaller grains, which are transported and deposited as sediments.
The
sediments or compacted and cemented and sedimentary rocks are formed.
Changes in
temperature and pressure can allow igneous and sedimentary rocks
to change
physically or chemically to form metamorphic rocks. At higher
temperatures,
metamorphic rocks may be partially melted, and crystallization
of this melt will
create igneous rocks. Uplift and erosion can expose all
rocks types at the
surface, re-initializing the cycle
(www.science.ubc.ca).