2. Rocks and Their Properties
Overview
1. What is a mineral?
2. What are the names of some minerals?
3. How are minerals different from rocks?
4. What are some of the physical properties of minerals that
can be tested?
5. Describe how the three main categories of rocks
(metamorphic, sedimentary, and igneous) are formed.
6. Describe the rock cycle.
3. What is a mineral?
Minerals are the building blocks of rocks. Rocks are
made of combinations of minerals.
Minerals are inorganic; they are not alive and they are
not plants or animals. An example of a rock that is not a
mineral is coal. Coal is a substance formed from decayed
plants and animals. Therefore, coal is not considered a
mineral.
Minerals are found in the earth or are naturally
occurring substances. They are found in dirt, rocks, and
water. They are not made by humans.
Minerals are chemical substances. Some minerals
like gold or silver are made of only one element. Other
minerals, like quartz and calcite, are combinations of two
or more elements.
Minerals always have the same chemical makeup.
For example, quartz will always consist of one part silicon
(an element) two parts oxygen (another element).
4. What are the names of some
minerals and rocks?
Minerals are usually solid crystals. They have
a number of flat surfaces in an orderly arrangement.
For example, a crystal of quartz is always
hexagonal because of the way the atoms of silicon
and oxygen join together.
About 2,000 minerals have been found. Oxygen
is part of many minerals. Minerals containing
oxygen make up almost half of the earth's crust.
Quartz is a common mineral. Other common
minerals are feldspar, mica, and horneblend.
Many rocks are made of these common minerals.
Some minerals are rare and expensive. They are
called gems . Diamonds, rubies, and emeralds
are good examples of such minerals. Gold and
silver are also minerals. Together, these natural
substances are used to make beautiful jewelry.
5. Mineral Versus
Rocks
How are minerals different from rocks?
Minerals have a single molecular
or atomic structure throughout.
Many are crystals, like quartz or
diamond. Others are metallic like
silver and gold. All are inorganic,
or non-living.
Rocks are made up of different
minerals. Their chemical
composition depends on the
minerals and other materials in
them. Rocks may include both
inorganic and organic material.
6. Mineral Tests
What are some of the physical properties of minerals that
can be tested?
hardness -- Hardness is a measure of a mineral's
resistance to abrasion (scratching) and reflects the
atomic structure of a mineral. It is measured using the
Mohs Hardness Scale. The mineral is scratched with
various objects, then rated on the Mohs Hardness Scale.
color – The color of a mineral is tested with the eyes.
luster – How a mineral reflects light is its luster. Look
at the mineral and use some of the following terms to
describe its luster: metallic, pearly, greasy, waxy, dull.
cleavage (shape) -- Cleavage describes how a
crystal breaks when subject to stress on a particular
plane or surface. If part of a crystal breaks due to stress
and the broken piece retains a smooth plane or crystal
shape, the mineral has cleavage. A mineral that never
produces any crystalline fragments when broken off has
no cleavage.
•
Finger Nail (H = 2.5)
•
Knife Blade (H = 5.5)
• Penny (H = 3)
7. Mineral Tests
What are some of the physical properties of
minerals that can be tested?
streak – Streak is the color of the mineral
when it is powdered. Using a white and a
black streak plate, the mineral is stroked
across the plate and the color observed with
the eyes.
magnetism – Magnetism is whether or not
the mineral attracts a magnet.
transparency -- The amount of light able
to be passed through a mineral determines
its transparency . Light is able to pass
through transparent minerals; translucent
minerals partially let light pass through; and
opaque minerals do not let any light through.
smell – The odor or smell of the rock.
8. What are the three categories of
rocks?
How are they formed?
Igneous rocks are formed from cooled magma
underground or lava from volcanoes above ground.
In the top picture, lava flowing from a volcano in
Hawaii forms igneous rocks.
Sedimentary rocks are formed underwater when
sediments like mud, sand, shells, and pebbles on
the ocean floor are pressed until they become rock.
In the middle picture, sedimentary and
metamorphic rocks in Arizona were broken into
sediments and carried away, leaving the Grand
Canyon behind.
Metamorphic rocks are formed when heat and
pressure transform igneous or sedimentary rocks.
In the bottom picture, metamorphic rocks in Arizona
show formerly flat sedimentary layers squeezed
into new shapes.
10. Soil
How is soil formed?
There are four basic “ingredients” that go into the “recipe” for making soil: tiny
pieces of rock (called inorganic material), decayed plants and animals (called
organic material), water, and air.
When small pieces of rock break off larger ones, they form the basis of all soil.
This breaking can occur through weathering and erosion:
weathering – rocks are broken into smaller pieces in two ways:
1.chemical weathering – when water dissolves or rusts away rocks
2.physical weathering – when wind, water, ice, temperature changes, glaciers,
animals, and plants break off pieces of rock
erosion – when smaller pieces of rock are moved away by water, wind, ice,
glaciers, rocks, etc.
11. Soil
Because soils develop under a variety of conditions, the soil in
one location can be very different from the soil in another
location. In order to understand soil and how one soil differs
from another, geologists look at and measure the soil’s
properties.
color – determined by the organic or inorganic materials
texture – the size of particles in the soil
water retention ability – determined by texture of particles
water and air content – determined by location of soil, as well
as its texture and composition
12. Weather
1. Describe the four main weather factors. (Remember our
acronym, WHAM: wind, heat, air pressure, and moisture.)
2. How do the main weather factors combine with geography
to create the weather in a particular place and season?
3. How do the revolution of the earth around the sun, the
earth’s rotation, and its tilt cause our seasons?
4. What are the various forms of precipitation?
5. What determines the type of precipitation that occurs?
6. How do global patterns such as the jet stream and water
currents influence local weather in measurable terms, such
as temperature, wind direction and speed, and
precipitation?
7. How are weather and climate the same and different?
13. Main Weather
Factors
Remember our acronym, WHAM: wind, heat,
air pressure, and moisture.
wind – the movement of air in a horizontal direction; local
winds (sea, land, and mountain breezes) are caused by local
geography, while global wind patterns (westerlies, easterlies,
jet stream) are caused by global rotation
heat – the sun’s energy travels to the earth as radiant
energy, which is light and heat, but this energy only raises
temperature when it encounters material
air pressure – the weight of air in a certain space or
altitude, caused by gravity holding the atmosphere down on
the Earth
moisture – water in the atmosphere
14. Weather and Geography
How do the main weather factors combine with geography to create the
weather in a particular place and season?
Local geography, like oceans, large lakes, and mountains can affect weather in an
area. Prevailing winds and presence or absence of the jet stream will also affect
weather. In MA, the Berkshire Hills in the west and the ocean in the east, westerly
prevailing winds, ocean winds, and the jet stream all affect local weather.
15. The Seasons
How do the revolution of the earth around the sun, the earth’s rotation,
and its tilt cause our seasons?
The 23o
tilt of the Earth as it revolves annually around the sun determines the
seasons. When a hemisphere is leaning toward the Sun, there are higher
temperatures and longer periods of daylight.
16. Forms of Precipitation
What are the various forms of precipitation?
Snow, rain, hail, and sleet are all forms of precipitation.
17. Forms of Precipitation
What
determines the
type of
precipitation
that occurs?
Temperature in
the clouds, in the
air through which
it falls, and on the
surface
determines the
form of
precipitation.
18. Forms of Precipitation --
Hail
How does hail form?
Hail forms in cumulonimbus
clouds when electrical charge
become unequal, temperatures
vary from below to above
freezing, and water droplets
move up and down in air
currents in these huge, tall
clouds.
19. Global Weather Patterns
How do global patterns such as the jet stream and water
currents influence local weather in measurable terms, such as
temperature, wind direction and speed, and precipitation?
The jet stream brings cooler air to the USA, while the Gulf Stream warms
the waters of Atlantic Ocean. Other parts of the world have different
ocean currents, jet stream, and other global wind patterns.
20. Weather and
ClimateHow are weather and climate the same and different?
The climate of a region is its weather over many months and years. Climates can
be described using terms like polar, temperate, and tropical. Massachusetts is in a
temperate climate zone.
21. The Water Cycle
• Describe the four parts of the water cycle? (Remember our acronym
CAPE: condensation, accumulation, precipitation, and evaporation
(terms not in order).)
• How does the water cycle affect the climate of a place?
