Unit 4 – Lesson 1
(Minerals)
Common Traits among Minerals
Mineral: a naturally occurring, usually inorganic solid that has a
definite crystalline structure and chemical composition.
Definite Chemical Composition
Chemical composition is determined when atoms (smallest,
indivisible particle of matter) of elements (pure substances) are
combined chemically to make compounds.
Definite chemical composition means that the arrangement of atoms
in the compound do not change.
Solid
Matter (anything that has volume and mass) that is in the solid state
has a definite volume and shape.
Usually Inorganic
Organic means that it is or once was alive.
Inorganic means that it does not come from living things and is
instead formed in the non-living environment.
Crystalline Structure
Crystal: a solid, geometric form that results from a repeating pattern
of atoms or molecules.
Crystalline structure means that the particular atoms of a specific
mineral solidify in a particular pattern.
Naturally Occurring
Minerals occur naturally in that natural processes form them; such
as evaporating water or high pressure deep underneath the Earth’s
surface.
How are Minerals Formed?
Minerals form through natural processes.
The type of mineral that forms is determined by the type of
chemical, the temperature of the area it is forming, and the pressure
of the area it is forming.
As Magma and Lava Cools
When a volcano erupts, it releases magma. Once cooled, that lava
forms many different kinds of minerals.
Metamorphism
At the high pressures and temperatures that exist under the Earth,
atomic bonds break between existing minerals are reform to make
new minerals with new crystalline structures.
From Solutions
Minerals can form as water evaporates.
◦ Minerals dissolved in water must precipitate on to solid surfaces.
◦ Hotter water forms minerals as well. Higher temperature water can
dissolve more substances.
Mineral Classification
Minerals are classified by composition:
◦ Silicate Minerals
◦ Nonsilicate Minerals
Silicate Minerals
Silicate Minerals are made up of a combination of silicon and oxygen
Both Silicon and Oxygen are very common in the Earth’s crust, so
naturally 90% of Earths minerals are silicate minerals.
Nonsilicate Minerals
Nonsilicate Minerals do not contain the silicon and oxygen tetrahedron.
These Minerals can be made up of elements such as carbon, oxygen,
fluorine, iron, and sulfur and only make up about 10% of the minerals
on Earth.
Classes of Nonsilicate Minerals
Native Elements: Minerals composed of one element.
Halides: Form when two highly reactive elements form a compound.
Sulfates: Minerals that contain both Sulfur and Oxygen.
Carbonates: Minerals containing both Carbon and Oxygen.
Oxides: When elements form bonds with Oxygen. ex – rust
Sulfides: Elements other than Oxygen form bonds with Sulfur.
Identifying Minerals
Just like you could discern what ingredients were used in a certain
dish by using your taste buds, you can identify mineral by specific
properties.
Identifying Minerals
Color:
◦ Color can identify minerals, but can also be deceiving.
◦ Ex. Impurities in quartz can lead to different colors in the crystal.
Identifying Minerals
Streak:
◦ The color of the powdered form of a mineral is known as streak.
◦ You can find out the color of a streak by rubbing the mineral across a
streak plate.
Identifying Minerals
Luster: the way a surface reflects light
◦ Describes the way that the surface of the mineral catches light. Which
colors are absorbed and reflected and in what way are the reflected?
Identifying Minerals
Cleavage and Fracture:
◦ Cleavage occurs when a mineral breaks along flat, parallel surfaces.
◦ Fracture occurs when minerals break unevenly
Identifying Minerals
Density:
◦ Density is measured by how much matter is packed into a given space.
◦ Every Mineral has a specific density. Measuring this density can help
distinguish between different minerals.
Identifying Minerals
Hardness: Mineral’s resistance to being scratched
◦ The Mohs scale helps determine the relative hardness of minerals.
Identifying Minerals
Special Properties:
◦ In addition to the previous methods for identifying minerals, some
minerals have special properties that distinguish it from others
◦ Ex. Magnetite is magnetic, Calcite causes a double image.