types of rocks
DESCRIPTION
Types of Rocks. Geologists place rocks into three groups according to how they form: igneous, sedimentary and metamorphic. Igneous Rocks. Igneous rocks were originally hot, fluid magma within the Earth. Igneous get their name from the Latin word, ignis , which means “fire”. Sedimentary Rock. - PowerPoint PPT PresentationTRANSCRIPT
Types of Rocks
• Geologists place rocks into three groups according to how they form: igneous, sedimentary and metamorphic.
Igneous Rocks
• Igneous rocks were originally hot, fluid magma within the Earth. Igneous get their name from the Latin word, ignis, which means “fire”.
Sedimentary Rock
• Most sedimentary rocks are formed from particles that have been carried along and deposited by wind and water. These particles, sediments or detritus, include bits of rock in the form of mud, sand or pebbles. Sediments also include shells, bones, leaves, stems and other remains of living things. Over time they are pressed together to form rocks.
Metamorphic Rocks
• Metamorphic rocks are formed when chemical reactions, tremendous heat and great pressure change existing rocks into new kinds of rocks. These new rocks have chemical and physical properties usually quite different from the original rocks.
Properties of MineralsGeologists use
characteristics to tell one mineral from
another
Mineral Properties we will study
Luster Hardness
Cleavage Streak
Luster• Refers to the way light
reflects from the surface of the mineral.
• There are two types of luster, –Metallic: looks like polished metal.
–Nonmetallic: does not look like polished metal. • Nonmetallic can be shiny or dull.
Pyrite has metallic luster
Quartz has nonmetallic luster
Hardness• Is measured by how easy it is to
scratch. • Geologists order the hardness by…1. Scratched by a fingernail.2. Scratched by a penny. 3. Scratched by a nail. 4. Scratched by a diamond. These are not all of the tools geologists
use, but it will work for our experiment.
Gypsum is soft, it can be scratched by a fingernail.
Calcite is soft, but a little harder because it cannot be
scratched by a fingernail, but it can be scratched by a penny.
Fluorite is harder. It can be scratched by a nail, but not a
penny or fingernail.
Diamonds are the hardest mineral, so it scratches every
mineral.
Cleavage• Not all minerals have
cleavage. • Some minerals split easily
along a flat surface. • The number of lines that are
created when a mineral is split will be the number of cleavage lines.
Mica has cleavage in one direction.
It breaks along one line.
Feldspar has two lines of cleavage. It breaks along
two lines.
Streak• Red chalk on a chalk board
makes red marks. White chalk makes white marks.
• Not all minerals work this way. When some minerals are scratched along a ceramic streak plate, it creates a different color.
Gold• When gold is
run across a streak plate it makes a yellowish-gold color.
• That makes sense.
Pyrite or “Fool’s Gold”• When pyrite is run
across a streak plate, it has a black or dark green streak.
• Pyrite is not worth much money, while gold is worth a lot. They look alike, so miners call it fool’s gold.
Hematite• Hematite’s color is
grey, but its streak is red.
• Hema means blood.
• The mineral was named hematite because it looked like it was bleeding when it was taken across a streak plate.
One mineral property we will
not use…COLOR
A mineral can be many different colors. Below is Mica.
Many minerals can be the same color. Below are gold colored minerals. Which one
is gold?
The answer…None of them
were real gold.
Just like with people…Outside color does not tell
you much about the important characteristics.