Transcript Slide 1

Halite is common table salt. It forms
where brakish (salty) lakes or sea beds
dry up. This evaporation of the water
causes the salt to precipitate forming
the salt crystals. Halite frequently
occurs in crystal form. It is usually
colorless but can be reddish brown
because of iron oxides in the water that
it forms in. Halite has perfect cleavage
and a hardness of 2.5 on the Mohs
hardness scale .
Limestone is the most abundant of the non-clastic
sedimentary rocks. Limestone is produced from the
mineral calcite (calcium carbonate) and sediment. The
main source of limestone is the limy ooze formed in the
ocean. The calcium carbonate can be precipitated from
ocean water or it can be formed from sea creatures that
secrete lime such as algae and coral.
Chalk is another type of limestone that is made up
of very small single-celled organisms. Chalk is
usually white or gray in color.
Limestone can easily be dissolved by acids. If you
drop vinegar on limestone it will fizz. Put a
limestone rock into a plastic jar and cover it with
vinegar. Cover the jar and watch the bubbling of
the calcium carbonate and also the disintegration of
the rock over a few days.
Sandstone is a clastic sedimentary
rock that forms from the cementing
together of sand sized grains
forming a solid rock. Quartz is the
most abundant mineral that forms
sandstone. Calcium carbonate, silica,
or iron has been added to the water
that is in contact with the sand
grains. These minerals grow crystals
in the spaces around the sand
grains. As the crystals fill the gaps
the individual sand grains are now
transformed into a solid rock
Chert is a very hard sedimentary rock
that is usually found in nodules in
limestone. Chert is light gray to dark
gray in color. It probably formed from
the remains of ancient sea sponges or
other ocean animals that have been
fossilized. Silica has replaced the
tissue forming the sedimentary rock.
Flint is a very dark form of chert. It
breaks like obsidian with conchoidal
fractures making it widely used by
ancient people to make arrowheads,
spear heads, and knives.
Conglomerate is a clastic sedimentary
rock that contains large (greater then
two millimeters in diameter) rounded
particles. The space between the
pebbles is generally filled with smaller
particles and/or a chemical cement
that binds the rock together. The
specimen shown above is about two
inches (five centimeters) across.
Limestone is a rock that is composed
primarily of calcium carbonate. It can
form organically from the accumulation
of shell, coral, algal and fecal debris. It
can also form chemically from the
precipitation of calcium carbonate from
lake or ocean water. Limestone is used in
many ways. Some of the most common
are: production of cement, crushed stone
and acid neutralization. The specimen
shown above is about two inches (five
centimeters) across.
Sandstone is a clastic sedimentary
Shale is a clastic sedimentary
rock made up mainly of sand-size
rock that is made up of clay-size
(1/16 to 2 millimeter diameter)
(less then 1/256 millimeter in
weathering debris. Environments
diameter) weathering debris. It
where large amounts of sand can
typically breaks into thin flat
accumulate include beaches, deserts,
pieces. The specimen shown
flood plains and deltas. The
above is about two inches (five
specimen shown above is about two
centimeters) across.
inches (five centimeters) across.
Andesite is a fine-grained,
extrusive igneous rock
composed mainly of
plagioclase with other
minerals such as
hornblende, pyroxene and
biotite. The specimen shown
is about two inches (five
centimeters) across.
Basalt is a fine-grained,
dark-colored extrusive
igneous rock composed
mainly of plagioclase and
pyroxene. The specimen
shown is about two inches
(five centimeters) across.
Diorite is a coarse-grained,
intrusive igneous rock that
contains a mixture of
feldspar, pyroxene,
hornblende and sometimes
quartz. The specimen shown
above is about two inches
(five centimeters) across.
Gabbro is a coarse-grained,
dark colored, intrusive
igneous rock that contains
feldspar, augite and
sometimes olivine. The
specimen shown above is
about two inches (five
centimeters) across.
Granite is a coarse-grained,
light colored, intrusive
igneous rock that contains
mainly quartz and feldspar
minerals. The specimen
above is about two inches
(five centimeters) across.
Obsidian is a dark-colored
volcanic glass that forms from
the very rapid cooling of molten
rock material. It cools so rapidly
that crystals do not form. The
specimen shown above is about
two inches (five centimeters)
across.
Pumice is a light-colored vesicular
igneous rock. It forms through
very rapid solidification of a melt.
The vesicular texture is a result
of gas trapped in the melt at the
time of solidification. The
specimen shown above is about two
inches (five centimeters) across.
Rhyolite is a light-colored,
fine-grained, extrusive
igneous rock that typically
contains quartz and
feldspar minerals. The
specimen shown above is
about two inches (five
centimeters) across.
Amphibolite is a non-foliated
metamorphic rock that forms
through recrystallization under
conditions of high viscosity and
directed pressure. It is
composed primarily of amphibole
and plagioclase, usually with very
little quartz. The specimen
shown above is about two inches
(five centimeters) across.
Gneiss is foliated metamorphic
rock that has a banded
appearance and is made up of
granular mineral grains. It
typically contains abundant
quartz or feldspar minerals. The
specimen shown above is about
two inches (five centimeters)
across.
Hornfels is a fine-grained nonfoliated metamorphic rock with no
specific composition. It is
produced by contact
metamorphism. Hornfels is a rock
that was "baked" while near a
heat source such as a magma
chamber, sill or dike. The
specimen shown above is about
two inches (five centimeters)
across.
Marble is a non-foliated
metamorphic rock that is
produced from the
metamorphism of limestone.
It is composed primarily of
calcium carbonate. The
specimen shown above is
about two inches (five
centimeters) across.
Phyllite is a foliate metamorphic
rock that is made up mainly of
very fine-grained mica. The
surface of phyllite is typically
lustrous and sometimes wrinkled.
It is intermediate in grade
between slate and schist. The
specimen shown above is about
two inches (five centimeters
across).
Quartzite is a non-foliated
metamorphic rock that is
produced by the
metamorphism of
sandstone. It is composed
primarily of quartz. The
specimen above is about
two inches (five
centimeters) across.
Schist is metamorphic rock with well
developed foliation. It often contains
significant amounts of mica which allow
the rock to split into thin pieces. It is a
rock of intermediate metamorphic
grade between phyllite and gneiss. The
specimen shown above is a "chlorite
schist" because it contains a significant
amount of chlorite. It is about two
inches (five centimeters) across.
Slate is a foliated metamorphic
rock that is formed through
the metamorphism of shale. It
is a low grade metamorphic
rock that splits into thin
pieces. The specimen shown
above is about two inches (five
centimeters) across.