What is a Mineral Chapter 3 Minerals of Earth’s Crust
Questions to ask yourself
• Is it a nonliving material?– A mineral is inorganic, meaning it isn’t made of living things
• Is it a solid– Minerals cant be gases or liquids
• Does it have a crystalline structure– Minerals are crystals, which have a repeating inner structure that
is often reflected in the shape of a crystal. Minerals generally have the same chemical composition throughout
• Is it formed in nature?– Crystalline materials made by people aren’t classified as
minerals.
What is a Compound made of?
• Compound- a substance made of TWO or more elements that have been CHEMICALLY combined.– Ex: Halite (NaCl)
Crystals • A solid whose atoms, ions, or
molecules are arranged in a definite pattern – Geometric forms of minerals produced by
a repeating pattern of atoms– Shape is determined by arrangement of
atoms
Two Groups of Minerals
• Most common classification of minerals is based on chemical composition.– Silicate Minerals – Nonsilicate Minerals
Silicate Minerals
• Minerals that contain a combination of silicon and oxygen as well as other elements.
• Make up more than 90% of the Earth’s crust
• Other common elements they combine with include: aluminum, iron, magnesium and potassium.
Common Silicate Minerals
Quartz
Feldspar
Mica
Nonsilicate Minerals
• Minerals that do not contain a combination of the elements silicon and oxygen.
• Some include carbon, oxygen, fluorine, and sulfur.
• Classes of nonsilicate minerals:– Native Elements – Carbonates– Halides – Oxides – Sulfates – Sulfides
HaliteSpinel Gypsum
GalenaPyrite Calcite
Hematite
Native Elements
• Minerals composed of only one element– Ex: copper, gold, silver – Used in communications and electronic
equipment
Carbonates
• Minerals that contain combinations of carbon and oxygen in their chemical structure.
• Used in cement, building stones and fireworks
Halides• Compounds that form when fluorine,
chlorine, iodine, or bromine combine with sodium potassium or calcium.
• Used in the chemical industry and in detergents
Oxides
• Compounds that form when an element such as aluminum or iron combines chemically with oxygen.
• Used to make abrasives, aircraft parts and paint
Sulfates
• Minerals that contain sulfur and oxygen
• Used in cosmetics, toothpaste, cement, and paint.
Sulfides• Minerals that contain one
or more elements, such as lead, iron or nickel, combined with sulfur.
• Used to make batteries, medicines, and electronic parts.
Identifying Minerals
• We use several different properties to help identify minerals– Color– Luster– Streak– Cleavage and Fracture– Hardness– Density– Special Properties
Color
• The same mineral can often come in a variety of colors
• Not the best way to identify a mineral
All 3 are Pyrite (fools gold)
Luster
• The way a surface reflects light
• Minerals have metallic, submetallic or nonmetallic luster– Shiny = metallic– Dull = submetallic or nonmetallic
Streak
• Color of a mineral in powdered form
• Found by rubbing the mineral against a piece of unglazed porcelain called a streak plate
• The color of the mineral’s streak is not always the same as the color of the mineral sample
• Good way to identify a mineral
Cleavage• The splitting of
a mineral along smooth, flat surfaces.
Fracture
Different types of minerals break in different ways. The way a mineral breaks is determined by the arrangement of its atoms.
The manner in which a mineral breaks along either curved or irregular surfaces
Hardness
• A minerals resistance to being scratched
• We use Mohhs Hardness scale to determine the hardness
• To identify a mineral scratch the surface of a mineral with the edge of one of the 10 reference minerals.
• If it scratches the reference mineral your mineral is harder
Density • Measure of how much matter is in a given
object
• Ratio of an objects mass to it’s volume
• Measured in grams per cubic centimeter
• Water is used as a reference because we know it has a density of 1g/cm3