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GEOLOGY
AN INTRODUCTION TO MINERALS
WHAT IS GEOLOGY?
• Earth is a dynamic planet. Processes that change Earth’s surface operated in the past much as they do
today. Evidence of past surface and climatic changes are indicated in the rock and fossil records.
• Rocks are composed of minerals.
• Rocks and minerals cycle through processes that change their form.
• Geology is the study of these things.
EARTH’S SURFACE
• Earth’s surface is changed in several different ways;
•
Heat flowing from the Earth’s hot interior toward the cooler surface (convection currents)
•
Atmospheric processes
•
Volcanoes and Earthquakes
•
Mountains building, weathering, erosion, deposition
• Lots of small changes happening over a long period of time can eventually add up to major changes in
Earth’s surface.
CHARACTERISTICS OF MINERALS
• Minerals are everywhere! Scientists have identified more than 4,000 minerals in Earth’s crust, although
the bulk of the planet is composed of just a few.
• A mineral is a naturally occurring, inorganic, solid, with a crystalline structure and a specific chemical
composition.
• A mineral must possess all of the following characteristics:
•
It must be naturally occurring
•
It must be inorganic
•
It must be solid
•
It must be crystalline, meaning it has a repeating arrangement of atoms
•
It must have a specific chemical composition
NATURALLY OCCURRING
• Minerals are made by naturally occurring processes, meaning those that occur in or on Earth.
• Minerals cannot be manmade
•
Some natural processes that form minerals are evaporation and cooling molten rock.
• Evaporation forms minerals when mineral-rich, saturated water changes from a liquid into a gas, leaving
behind the minerals. (Great Salt Lake
• Cooling molten rock (magma or lava) forms minerals when the molten material solidifies into crystals.
•
A diamond created deep in the Earth’s crust by cooling magma is a mineral, but a diamond made in a laboratory
by humans is not.
INORGANIC
• The easiest way to understand inorganic is to put a definition to organic, because inorganic literally
means “not organic”
• Organic substances are made by living creatures and include proteins, carbohydrates, and oils.
• Inorganic substances are not made from living creatures.
• Coal is made of plant and animal remains. Is it a mineral?
•
Coal is classified as a sedimentary rock, but is not a mineral, because minerals cannot be directly made from
living organisms.
SOLID
• A solid is a substance that is rigid and holds its shape. It is not liquid nor gas, and is therefore not fluid.
• Minerals are “crystalline” structures. A crystal is a solid in which the atoms are arranged in a regular,
repeating pattern.