Download Sedimentary rocks

Rocks and Minerals
Across
5. rocks that are formed when magma cools
7. light reflected from a mineral
8. these rocks may be made up of only one mineral
9. example of a metamorphic rock
10. made up of two or more minerals
11. rocks that are formed when small pieces of earth have been
worn away
Down
1. ability to resist scratching
2. example of sedimentary rock
3. these occur naturally
4. rocks that change due to heat and pressure
6. shows the three types of rocks
Rocks and Minerals
Rocks
A rock is made up of two or more minerals. Rocks can be found everywhere, from under deep
oceans and in high mountain ranges to the ground beneath your feet.
To show how rocks slowly change over time, we use the Rock Cycle. The Rock Cycle shows
the three types of rock – igneous, metamorphic, and sedimentary.
Rocks can change by many processes. Rocks change slowly over time. Any given rock can
change into any of the three major rock types.
Sedimentary
Sedimentary rocks can be formed when small pieces of the earth have been worn away by wind and
water and they eventually form a rock at the bottom of a river, lake or ocean. Sedimentary rocks are
made from particles of sand, shells, pebbles, and other pieces of material. Together, all these particles
are called sediment.
Examples of this rock type include limestone, sandstone and coal.
Metamorphic
Metamorphic rocks are formed under the surface of the earth from the metamorphosis (change) that
takes place due to intense heat and pressure (squeezing). Pre-existing rocks (rocks that already exist)
are changed by heat and pressure.
Examples of this rock type include marble, slate and soapstone.
Igneous
Igneous rocks are formed when magma (molten rock deep within the earth) cools and hardens.
Sometimes the magma cools inside the earth, and other times it erupts onto the surface from volcanoes
(in this case, it is called lava).
Examples of this rock type include basalt, granite and pumice.
Characteristics of the Three Types of Rocks
Igneous rocks generally have no layers, have variable (different) textures, and do not contain
fossils. When lava cools very quickly, no crystals form and the rock looks shiny and glasslike.
Sometimes gas bubbles are trapped in the rock during the cooling process, leaving tiny holes and
spaces in the rock.
Metamorphic rocks may have alternating bands of light and dark minerals, or may be made up
of only one mineral such as marble or quartzite, and rarely contain fossils. The rocks that result
often have ribbon like layers and may have shiny crystals, formed by minerals growing slowly over
time, on their surface.
Sedimentary rocks often have flat layers, are made up of pieces that are roughly the same size
with pores (small spaces) between these pieces that are filled with smaller grains, and sometimes
contain fossils. You can often see sand, pebbles, or a stone in the rock and it is usually the only type
that contains fossils.
Fossils
Gas Bubbles
Crystals
Glassy Surface Ribbon like Layers
Sand or Pebbles
Minerals
Minerals must occur naturally. When something is naturally occurring, it means that people did
not make it. Steel is not a mineral because it is produced by people. Minerals are made of the same
substance throughout.
A variety of tests are used to identify the properties of minerals including: colour, hardness,
luster and streak.
The colour of a mineral is the first thing most people notice, but it can also be the least useful in
identifying a mineral. Most minerals occur in more than one colour.
The streak of a mineral is the colour of the powder left on a streak plate (piece of unglazed porcelain)
when the mineral is scraped across it.
Luster refers to how light is reflected from the surface of a mineral.
The hardness of a mineral is its ability to resist scratching.