2. The Minerals
Minerals are a collection of one or
more elements that are stacked neatly
together in a form called crystal
structure. They are stable at room
temperature, has an ordered atomic
structure and representable by a
chemical formula.
3. How minerals are being
formed?
Minerals are formed either by high
heat and high pressure existing
beneath the lithosphere or by natural
process like evaporation and
precipitation. Halite and gypsum are
formed through evaporation.
4. General properties of
Minerals
Minerals are solid.
Minerals have a definite chemical
composition.
Minerals have a definite shape.
Minerals are inorganic.
When minerals dissolve in liquid, it
loses its crystalline property and thus
cease to exist as mineral.
6. 1. Color – the first thing to be noticed in a
mineral. Basic way of identifying minerals
are by color.
Galena is
black
Elbaite is turquoise green.
Apatite is
lemon yellow
7. 2. Streaks – refers to the color of the
powder on a mineral when rubbed in a
hard, white piece of unglazed porcelain.
8. 3. Hardness – the ability of one mineral to scratch
another. The softer mineral gets scratched. The
hardest mineral is diamond and the softest is talc.
9. 4. Luster – refers to the ability of minerals to
reflect light.
5. Cleavage – is the flat surface along
which minerals split.
This sample of fluorite shows a smooth
cleavage face on the left where the
mineral broke along the plane of its cubic
crystal structure.
10. 6. Texture – refers to how minerals feel to
the touch.
11. Classification of Minerals
Silicates – compounds of silicon and
oxygen. Makes up 96% of the earth’s
crust.
Carbonates – compounds formed with
the carbonate group. It is the principal
mineral in limestone. Calcite is the most
common example of a mineral which
belong to the carbonates.
Sulfates – are compound formed with
sulfate group. Gypsum is the most
abundant rock forming sulfate.
12. Halides – compounds formed from
halogen and sodium, potassium or
calcium. Halite is the most common
example as it is a table salt or sodium
chloride.
Oxides – compounds of oxygen and other
elements. Most common are the oxides of
iron and aluminum. Hermatite is ferric
oxide.
Sulfides – are minerals containing one or
more metals combined with sulfur.
13. Crystal Systems
The crystal pattern of minerals is
controlled by the internal arrangement
of the atoms that make up the mineral.
Some examples of these crystal
structures are quartz which has a
hexagonal (six-sided) crystal and
halite which has a cubic crystal.
16. Rocks
Makes up the solid part of the earth’s
crust.
Usually made up of one or more
minerals. Some are made by only one
mineral.
Coal is special kind of rock.
18. Igneous Rocks
The word “igneous” comes from a
Greek word which means fire.
Oldest of all types of rocks.
Contains no fossils.
Rarely reacts with acid.
Usually has no layering.
Usually made of of two or more
minerals.
May be light or dark-colored.
Has glass fibers.
19. Examples of Igneous Rocks:
Granite – composed of quartz, feldspar, mica, and
hormblende. Granite forms as magma cools far
under the earth’s surface. It cools very slowly.
Basalt – dark-colored, fine grained extrusive
rock. The mineral grains are so fine that they
are impossible to distinguish with the naked
eye or even a magnifying glass.
Gabbro – dark-colored, coarse-grained
intrusive igneous rock. Composed mostly of
plagioclase feldspar with small amount of
pyroxene and olivine.
20. Rhyolite – very closely related to granite only that it
has much finer crystals. These crystals are so small
that they cannot be seen by the naked eye. Rhyolite
cooled much more rapidly than granite giving it a
glassy appearance.
Pumice – light-colored, frothy volcanic rock.
Formed from lava that is full of gas. During
eruption, as the lava hurtles through the air, it cools
and the gases escape leaving the rock full of holes.
Obsidian – very shiny natural volcanic glass.
When an obsidian breaks, it fractures with a
distinct conchoidal fracture. Obsidian is
produced when lava cools very quickly that no
crystals can form.
21. Two Types of Igneous rocks:
Intrusive – igneous rocks that cools
slowly deep beneath the earth’s surface.
The slow cooling results to formation of
large crystals. Granite is an example of
an intrusive igneous rock.
Extrusive – igneous rocks that cools very
quickly as the lava is erupted or magma
reaches the surface. Obsidian and basalt
are two examples of extrusive igneous
rocks. They are commonly shiny and
glassy.
22.
23. Sedimentary Rocks
Formed through erosion and other
weathering agents such as wind, water and
ice.
Often contains fossils.
Reacts with acid.
Has layers, flat or curved.
Composed of pieces cemented or pressed
together.
Has great color variety.
Has pored between pieces.
May have cross-bedding, mud cracks, worm
burrows, raindrop impressions.
25. Conglomerate – a clastic sedimentary rock that is formed from the
cementing of rounded cobble and pebble sized rock fragments.
Formed by river movement or ocean wave action.
Chert – a very hard sedimentary rock that is commonly found in
nodules in limestone. Chert is dark gray to light gray in color. It
probably formed from the remains of ancient sea sponges or other
ocean animals fossilized.
Limestone – the most abundant of the non-clastic sedimentary rocks.
Limestone is produced from the mineral calcite and sediment.
Sandstone – is a clastic sedimentary rock that forms from the
cementing together of sand sized grains forming a solid rock.
Shale - Shale, common name applied to fine-grained varieties of
sedimentary rock formed by the consolidation of beds of clay or mud.
Most shales exhibit fine laminations that are parallel to the bedding
plane and along which the rock breaks in an irregular, curving
fracture. Shales are usually composed of mica and clay minerals.
Arkose - a coarse-grained sedimentary rock rich in feldspar and
quartz.
26. Three Types of Sedimentary
Rock:
Clastic rocks - form from clasts, or
broken fragments, of pre-existing
rocks and minerals.
Chemical rocks - form when minerals
precipitate, or solidify, from a solution,
usually seawater or lake water.
Organic rocks - form from
accumulations of animal and plant
remains.
27.
28. Metamorphic Rocks
Comes from Greek words meaning “change”
and “form”.
Formed deep in the earth where high
temperature, great pressure, and chemical
reactions cause one type of rock to change
into another type of rock.
Metamorphic rocks begin to form at 12-16
kilometers beneath the earth’s surface.
They begin changing at temperatures of 100
degrees Celsius to 800 degrees Celsius.
Reacts with acid.
Rarely has pores or openings.
May have bent or curved foliation.
30. Marble – metamorphosed limestone or dolomite. Comes in
many color (white, red, black, mottled and banded, gray, pink,
and green.)
Slate – a fine-grained metamorphic rock with perfect cleavage
that allows it to split into thin sheets. Slate usually has a light
to dark brown color.
Schist – a medium grade metamorphic rock. It is more
subjected to more heat and pressure than slate, which is a
low grade metamorphic rock.
Gneiss – a high grade metamorphic rock. It is more subjected
to heat and pressure than schist.
Quartzite – composed of sandstone that has been
metamorphosed. Quartzite is much harder than the parent
rock, sandstone. It forms from sandstone that has come into
contact with deeply buried magmas.
33. Fossils
Fossil, remains or traces of prehistoric plants
and animals, buried and preserved in
sedimentary rock, or trapped in organic
matter. Fossils representing most living
groups have been discovered, as well as
many fossils representing groups that are
now extinct. Fossils range in age from 3.5-
billion-year-old traces of microscopic
cyanobacteria (blue-green algae) to 10,000-
year-old remains of animals preserved during
the last ice age. Paleontologists (scientists
who study prehistoric life) use fossils to learn
how life has changed and evolved throughout
earth’s history.
34. Body Fossils
It refers to the preserved remains of
an animal or plant’s body.
The most common body fossils
include bones, teeth, eggs and skin.
But the skin is less dense compared to
the three mentioned body fossils and
that it is easily decomposed.
35. Trace Fossils
Trace fossils are everything else that
the dinosaurs and our ancestors left
behind that are not part of their body
including footprints, egg shells, nests,
and game trails.
Scientists are able to learn additional
information about dinosaurs from
these traces that they cannot
accurately gain from body fossils
alone.
37. Carbonization
Plants are most commonly fossilized through
carbonization. In this process, the mobile oils
in the plant’s organic matter are leached out
and the remaining matter is reduced to a
carbon film. Plants have an inner structure of
rigid organic walls that may be preserved in
this manner, revealing the framework of the
original cells. Animal soft tissue has a less
rigid cellular structure and is rarely preserved
through carbonization. Although
paleontologists have found the carbonized
skin of some ichthyosaurs, marine reptiles
from the Mesozoic Era (240 to 65 million
years before present), the microscopic
structure of the skin was not preserved.
38. When plants are preserved through carbonization, the oils in the plant
gradually leach out, leaving a carbon film. The rigid walls of plant cells
preserved in this manner reveal the original cellular structure of the ancient
plant.
39. Petrifaction
Another common mode of preservation of
plants is petrifaction, which is the
crystallization of minerals inside cells. One of
the best-known forms of petrifaction is
silicification, a process in which silica-rich
fluids enter the plant’s cells and crystallize,
making the cells appear to have turned to
stone (petrified). Famous examples of
silicification may be found in the petrified
forests of the western United States (Petrified
Forest National Park). Petrifaction may also
occur in animals when minerals such as
calcite, silica, or iron fill the pores and cavities
of fossil shells or bones.
40.
41. Replacement
Replacement occurs when an organism is buried in
mud and its remains are replaced by sulfide (pyrite) or
phosphate (apatite) minerals. This process may
replace soft tissue, preserving rarely seen details of
the organism’s anatomy. X-ray scanning of some
German shales from the Devonian Period (410 million
to 360 million years before present) have revealed
limbs and antennae of trilobites (extinct ocean-dwelling
arthropods) and tentacle arms of cephalopods (highly
developed mollusks) that have been pyritised
(replaced by pyrite). Paleontologists have used mild
acids to etch the phosphatized fossil remains of
ancient fish found in Brazil to reveal structures such as
gills and muscles. Although mineral replacement is
rare, fossils created in this way are important in helping
paleontologists compare the anatomical details of
prehistoric organisms with those of living organisms.
42.
43. Recrystallization
Many animal shells are composed of the
mineral aragonite, a form of calcium
carbonate that breaks down over millions of
years to form the more stable mineral calcite.
This method of preservation, called
recrystallization, destroys the microscopic
details of the shell but does not change the
overall shape. Snail shells and bivalve shells
from the Jurassic Period (205 million to 138
million years before present) and later are still
composed principally of aragonite. Most older
shells that have been preserved have
recrystallized to calcite.
44.
45. Soft-tissue Preservation
The soft tissues of animals are preserved only under
extremely unusual conditions, and the preserved tissue
usually lasts for only a short period of geological time. In the
Siberian permafrost (earth that remains frozen year-round),
for example, entire mammoths have been preserved in ice for
thousands of years. The remains of the mammoths’ last
meals have sometimes been preserved in the stomachs,
allowing paleontologists to study the animals’ diet.
Mummification may occur in hot, arid climates, which can
dehydrate organisms before their soft tissue has decayed
fully. The skin itself is preserved for only a short time, but the
impressions of the skin in the surrounding sediment can be
preserved much longer if the sediment turns to rock.
Paleontologists have found skin impressions of dinosaurs
preserved by this method.
46.
47. Organic Traps
Whole organisms may become trapped and preserved in amber,
natural asphalt, or peat (decaying organic matter). Amber is the
fossilized remaining part of tree sap. When sap first flows from the
tree, it is very thick and sticky, so as it runs down the trunk, it may
trap insects, spiders, and occasionally larger animals such as
lizards. These organisms can be preserved for millions of years with
details of their soft tissue, such as muscles and hair-like bristles, still
intact.
Natural asphalt (also called tar) is a residue from oil that has seeped
to the earth’s surface from deposits in the rock below. When an
asphalt pit is covered by water, thirsty animals that come to the pit to
drink may become trapped in the sticky substance and be
preserved. One well-known example of such an area is the La Brea
Tar Pits of the Pleistocene Epoch (1.6 million to 10,000 years before
present) in Los Angeles, California.
Animals may also be preserved in peat, although the acidic
environment of this decaying organic matter may cause bones to
lose their rigidity. Some human remains have been found in peat
bogs in Denmark (2000 years old) and England (2200 years old).
48. Paleontologists can learn about prehistoric life by studying the remains of
ancient insects, such as this midge fly, trapped in tree resin when they were
alive. The resin eventually hardens and fossilizes into amber. Occasionally
whole organisms are preserved in this manner.
49. Molds and Casts
Acidic conditions may slowly dissolve away
the skeleton of fossil animals preserved in
rock, leaving a space where the organism
used to be. The impression that is left in the
rock becomes a mold. This process
commonly occurs in fossil shells where the
calcite shell dissolves easily. The impression
of the outside of the shell is the external
mold. Sometimes the inside of the shell is
filled with sediment before the shell is
dissolved, leaving an internal impression of
the shell called an internal mold. If the space
where the shell used to be is then filled with
a new mineral, the replica of the shell forms
a cast.
50. Although trilobites became extinct about 250 million years ago, their
fossilized casts can be found in rock formations. This silica shale formation
shows several trilobites. Because these primitive arthropods were typical
organisms of the Paleozoic era, a paleontologist may use them to determine
the relative age of the rock strata.
51. Track and Trails
When animals walk through soft
sediment such as mud, their feet, tails,
and other body parts leave impressions
that may harden and become preserved.
When such an impression is filled with a
different sediment, the impression forms
a mold and the sediment that fills the
mold forms a cast. Molds and casts of
dinosaur tracks are relatively common
and help paleontologists understand how
these creatures moved.
52. When dinosaurs walked through soft sediments or mud, the ground
occasionally hardened quickly enough to preserve their footprints.
Paleontologists use dinosaur footprints to learn about how dinosaurs
walked and their patterns of movement. These prints, found in Arizona,
were made by a theropod dinosaur from the Jurassic Period. Most
theropods walked on two legs and were carnivorous.
