Rocks can be divided
into three groups:
1. Igneous: Rocks
with crystals that have fomed by
moten magma cooling above or below
the earth's surface.
2. Sedimentry: Broken
fragments of older rocks that have
been cemented together.
3. Metamorphic: Rocks
that hae been altered by the effects
of heat and pressure.
: Igneous means made by fire. These
rocks are found deep underground
near to molten rock from inside
Igneous rock is formed
through the cooling and solidification
of magma or lava. Molten rock
is called magma. When it is
forced to the Earth's surface it
is also called lava. Lava
cools quickly on the surface to
form igneous rocks with small crystals.
Some magma gets trapped
and cools underground to form igneous
rocks which have large crystals. Some
igneous rocks are changed into metamorphic
rocks. Granite and basalt are
very hard, expensive, impermeable
and have muticolored, small particles.
Granite - is a
common, coarse-grained, light-colored,
hard igneous rock consisting chiefly
of quartz, orthoclase or microcline,
and mica. It is used in monuments
and for building.
Basalt - is a common
extrusive volcanic rock. It
is usually grey to black and fine-grained
due to rapid cooling of lava at the
surface of the planet. Unweathered
basalt is black or grey.
rocks : is a type
of rock that is formed by sedimentation
of material at the Earth's
surface and within bodies of
water. These rocks are
made from sediment on the sea
Particles that form
sedimentary rock by accumulating are
called sediment. These rocks are soft
and crumbly, often have layers and
fossils can be found in them. Sediment
is formed by weathering and erosion
in a source area and then transported
to the place of deposition by water,
wind, mass movement or glaciers which
are called agents of denudation.
The layers of sediment
gradually get squashed and eventurally
form sedimentarty rock. They
are permeable. Some sedimentary
rocks get heated and squashed under
the surface of the Earth.
This changes the rock
into metamorphic rock.
Conglomerate, Limestone, Mudstone
Chalk - is a soft,
white, gray, or yellow limestone consisting
mainly of calcium carbonate and formed
primarily from the accumulation of
fossil microorganisms such as foraminifera
and calcareous algae.
Conglomerate - rock
has pieces of other rocks glued together
to form one larger rock. These
rocks are found along rivers, beaches
and glaciers where water or ice drops
them. This rock is made up of
pebbles and other small gravel and
sand glued together with iron oxice,
calcium carbonate or silica.
Limestone - is a
sedimentary rock consisting mostly
of calcium carbonate. It is used as
a building stone and in the manufacture
of lime, carbon dioxide, and cement.
Mudstone - is a
fine grained sedimentary rock whose
original constituents were clays
or mud. Individual grains are too
small to be seen without a microscope
- grain size is up to 0.0625 mm
Sandstone - this
rock can be scratched easily.
It is formed by the consolidation
and compaction of sand and held together
by a natural cement, such as silica.
rocks – these
rocks characteristics have
been altered or changed (Metamorphism)
over time by great pressure
from layers of rock above them
and heat below them or chemical
changes affecting pre-existing
rocks. Metamorphism is
the process by which an existing
rock is changed through the
action of heat and pressure.
These rocks have been
changed in the earth by heat
They are impermeable.
These rocks were once igneous or
sedimentary rocks. They are hard and commonly
used in building materials.
Marble, Quartzite & Slate :
Gneiss - ["nice"]
is a rock of great variety with large
mineral grains arranged in wide bands.
It means a type of rock texture, not
a composition. It is a common
and widely distributed type of rock
formed by high-grade regional metamorphic
processes from pre-existing formations
that were originally either igneous
or sedimentary rocks.
Marble - A metamorphic
rock formed by alteration of limestone
or dolomite, often irregularly colored
by impurities, and used widely in
architecture and sculpture.
Quartzite - is a
hard metamorphic rock which was originally
sandstone. Sandstone is converted
into quartzite through heating and
pressure usually related to tectonic
compression within orogenic belts.
Pure quartzite is usually white to
grey, though quartzites often occur
in various shades of pink and red
due to varying amounts of iron oxide.
Other colors, such as yellow and orange,
are due to other mineral impurities.
When sandstone is metamorphosed to
quartzite, the individual quartz grains
recrystallize along with the former
cementing material to form an interlocking
mosaic of quartz crystals.
Most or all of the original texture
and sedimentary structures of the
sandstone are erased by the metamorphism
that occured. Small amounts of former
cementing materials, iron oxide, carbonate
and clay, often migrate during recrystallization
and metamorphosis. This causes streaks
and lenses to form within the quartzite.
Slate - is grey
and quite smooth fine-grained metamorphic
rock.. Easily splits into thin
and smooth-surfaced layers.
Quartzite (view 1)
Quartzite (view 2)
Rocks - allow water to pass through
Rocks - are rocks that are waterproof.
Acid, Cliff, Cracks,
Crumble, Crystals, Deposited, Earth
Erosion, Fossil, Frost, Geologist,
Geology, Glacier, Grains,
Granite, Hard, Humus, Igneous, Limestone,
Marble, Metamorphic, Mineral, Molten,
Sample, Sedimentary Sediment, Smooth,
Soil, Stalactite, Temperature Transport,
Coal - is
a rock which can be burned as fuel. Coal
is called 'fossil fuel' because it
has formed from remains of trees
and plants from millions of years
A fossil - is
the remains of an animal or plant
that has been preserved in rocks. The
shapes and details of fossils show
us what the creature or plant looked
like when it was alive.