Geology Day 7: Rock Stations
STATION 1
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Name of Rock: ___________________________
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Name of Rock: ___________________________
Name of Rock: ___________________________
Drawing:
Observations:
1._____________________________________________________________________________________
2._____________________________________________________________________________________
Inference: It is a _______________________________ rock because
______________________________________________________________________________________.
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Name of Rock: ___________________________
Drawing:
Observations:
1._____________________________________________________________________________________
2._____________________________________________________________________________________
Inference: It is a _______________________________ rock because _____________________________________________________________________________________.
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Name of Rock: ___________________________
Drawing:
Observations:
1._____________________________________________________________________________________
2._____________________________________________________________________________________
Inference: It is a _______________________________ rock because
______________________________________________________________________________________.
.
Rock #1
Name of Rock:
Sandstone
Description: Sandstone
is a clastic (composed of smaller fragments) rock made up mostly of sand-sized
particles called grains. Most sandstone is formed from grains deposited from
actively moving water, such as waves on a beach or the channel in a river. The
grains are typically cemented together by silica or calcite to form the
sandstone rock. Sandstone is most commonly composed of quartz grains because
quartz is a common mineral that is resistant to abrasion.
Sandstone’s color is commonly buff to brown, can also be red
because of the presence of iron oxides or green because of the presence of
glauconite.
Sandstone has many uses in the construction industry as
aggregate (collective) and building stone. The Hickory Sandstone, located in
Central Texas, is high-grade
(quartz-rich) sandstone that is quarried as a material in the making of glass.
The sandstone sample in the Texas Rock Kit was collected
from the Llano Uplift and is Cambrian in age.
Rock #2
Name of Rock:
Basalt
Description: Basalt
is an extrusive rock. Extrusive (volcanic) rocks form when molten rock, which
has erupted from the Earth's interior through a volcano or crack in the Earth,
cools rapidly at the surface. The rapid cooling does not typically allow
mineral crystals to grow large enough to be seen by the unaided (without a
magnifying glass) eye, so texture is typically fine grained.
Basalt is dark-gray to almost black. It is very hard and
fine grained. The common minerals in basalt are plagioclase (feldspar),
pyroxene, and olivine. Some of these minerals may occur as phenocrysts (large
grains).
Much of basalt in Texas is exposed in eroded volcanoes. A
string of basaltic volcanoes were active in the Late Cretaceous in Central and
South Texas, around 80 to 100 million years ago, and much younger basalts occur
at several locations in the Trans-Pecos. Basalt is used as roadbed material for
railroad tracks in many places in Texas and is commonly called trap rock.
The basalt sample in the Texas Rock Kit was collected in
Uvalde County and is Cretaceous in age. In Texas, no volcanoes are considered
to be currently active.
Rock #3
Name of Rock: Schist
Description: Schist is a common rock with a
well-developed foliation (layered
2-D texture) that is due to the presence of aligned platy
(crystalized thin sheets that flake when touched) minerals such as mica and/or
talc. The pressure in the mantle where this rock was formed arranges the platy
minerals so that the flat planes of the mineral flakes are approximately
parallel to one another.
Some non-platy minerals, such as garnets, may also be
present. Schist can form from basalt (igneous rock), shale (sedimentary rock),
or slate (metamorphic rock that forms at lower temperatures and pressures).
Certain varieties of schist are quarried or gathered from
rock pits for talc, which is used in ceramic glazes, paint fillers, and roofing
materials, as well as carriers for insecticides. Vermiculite (a type of mica)
from schist in Llano County can be processed to be as potting soil.
The schist sample in the Texas Rock Kit was collected from
the Llano Uplift and is Precambrian in age.
Rock #4
Description: Limestone
is a "chemically" weathered rock that is composed mostly of calcite
(CaCO3) that precipitates (grows rapidly) from seawater. Limestone, the most
common chemically weathering rock in Texas, is most commonly white to gray
color. Because the dominant mineral is calcite, limestone reacts with a strong
effervescence (fizz or tiny gas bubbles) when tested using a dilute acid such
as hydrochloric acid or vinegar. Groundwater is slightly acidic and, hence,
slowly dissolves limestone. This process has produced the caves of Texas.
Variations of limestone include marl, a muddy limestone, and
chalk, a limestone composed of microscopic calcareous algae and tiny shells of
marine organisms. Limestone is common in the Hill Country and the Trans-Pecos
of Texas. Limestone in Texas is quarried or dug from a rock pit for cement,
aggregate or collective, and building stone. High-calcium-content limestone is
used in water purification and sewage treatment.
The limestone sample in the Texas Rock Kit was collected in Travis
County and is Cretaceous in age.
Rock #5
Description: Gneiss
(pronounced nice), a very common rock made up mostly of quartz and feldspar,
can also contain some mica. Gneiss is commonly crudely banded with layers
defined by light and dark minerals. Gneiss can develop from granite or a
clastic (rock fragment) sedimentary rock that has been heated and pressurized.
Gneiss in Texas is exclusively Precambrian in age. It can be used as aggregate
or building stone.
Rock #6
Description:
Granite is an intrusive rock. Intrusions (plutons or masses of this type of
rock) are bodies of rock that result from crystallization of magma deep
underground. Slow cooling at this depth in the Earth produces larger crystals
(coarse grained) that can easily be seen by the unaided eye.
Granite is generally light colored in shades of white, grey,
or pink. Minerals are mostly quartz and feldspar, with small amounts of mica
(muscovite or biotite).
Granite in Texas is found in the Llano Uplift of Central
Texas and the Trans-Pecos of West Texas.
The Town Mountain Granite, the most famous granite in Texas,
was used to construct the State capitol building, as well as many other State
office buildings in Austin. Granite in Texas is quarried for building stone and
aggregate.
The granite sample found in the Texas Rock Kit was collected
from the Llano Uplift and is Precambrian in age.
Station 2 - RockWriting
Station
3 – Stemscopes –
Web Surfing Science
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