MINERALS: The Building Blocks of Rocks! S6E5.b Investigate the composition of rocks in terms of...
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Transcript of MINERALS: The Building Blocks of Rocks! S6E5.b Investigate the composition of rocks in terms of...
MINERALS: The Building Blocks of
Rocks!S6E5.b Investigate the composition of rocks in terms of minerals.
WHAT IS A MINERAL?
• A mineral is a naturally formed, inorganic solid that has a definite crystalline structure.
Let’s Break it Down!!!
• Naturally formed = made in nature/not “man-made”.
• Inorganic = non-living• Solid = 3 dimensional, hard• Definite crystalline structure =
made of two or more elements; forms crystals.
Crystals
• Solid• Geometric (cubes, hexagons,
etc.)• Repeating pattern of atoms or
molecules
How Many Minerals Have Geologists Discovered?
• Geologists have discovered over 2,500.
• However, we only see about 100 frequently.
• Less than 20 are widely distributed.
2 types of minerals
Silicate
-contain a combo of silicon, oxygen and one or more metals
-make up 90% of earth’s crust
-quartz, mica
Nonsilicate
-does not contain compounds of silicon and oxygen
-copper, calcite, galena
IDENTIFYING MINERALS
• Color• Luster• Streak• Cleavage & Fracture• Hardness• Density• Special Properties
COLOR• What you see on the outside!• Not the best way to identify a mineral• Same mineral can come in a variety of
colors• Ex: Quartz---purest state is clear;
impurities can cause it to be different colors
• Exposure to air & water can change color (Ex: pyrite---usually golden but changes to brown or black when exposed to air & water)
LUSTER• Luster: the way a surface reflects
light; whether a mineral is shiny or dull!
• Metallic, submetallic or nonmetallic luster
• Shiny = metallic luster• Reflective/dull = submetallic• Dull= nonmetallic luster
STREAK• Streak: color of a mineral in
powdered form• Rub mineral against a piece of
unglazed porcelain (streak plate)• Mark left on streak plate is the
streak.• Color of streak not always the color
of the mineral sample.• Not affected by air or water• More reliable than color in identifying
a mineral
CLEAVAGE & FRACTURE• How a mineral breaks• Determined by arrangement of
atoms• Cleavage: tendency to break
along smooth, flat surfaces (Ex: halite & mica)
• Fracture: tendency to break unevenly along curved or irregular surfaces (Ex: quartz)
HARDNESS• Mineral’s resistance to being
scratched• Mohs Hardness Scale• Ranges from 1 to 10; 1 being softest
(talc) & 10 being the hardest (diamond)
• Scratch tests; scientists use common items to test hardness.– Fingernail has a hardness of 2-2.5– Knife blade is 3-4– Glass is 5-6– Steel file or nail is 6.5-7
A mineral of a given hardness will scratch any mineral that is softer than it is.
DENSITY• The measure of how much
matter is in a given amount of space.
• Density is a ratio of an object’s mass compared to it’s volume.
• D=m/v• Measured in grams per cubic
centimeter (g/cm3)
DENSITY• Water has a density of 1g/cm3
• Used as a reference point for other substances.
• Object sinks---it’s density is greater than 1g/cm3
• Object floats---it’s density is less than 1g/cm3
SPECIAL PROPERTIES• Only a few minerals have
these!• Fluorescence• Chemical reaction• Optical properties• Magnetism• Taste• Radioactivity
Most Common Rock-Forming Minerals
Quartz (SiO2)Calcite (CaCO3)Augite (Ca, Na)Hematite (Fe2O3)MicasFeldspars
Where do we get minerals?
• Open pits-quarries (above ground)
• Mine shafts (below earth)
Reclamation
• The process when land is returned to its original state or better
• Reduces harmful effects of mining
Uses of minerals:
• Copper—electrical wire• Gold—jewelry• Galena--batteries
Gemstones
• Nonmetallic mineral• Valued for their beauty and
rarity• Diamonds, ruby, sapphire,
emerald, aquamarine, topaz