MINERALS: The Building Blocks of Rocks! S6E5.b Investigate the composition of rocks in terms of minerals.

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