Minerals

Definition: A mineral is

• naturally occurring

Made by Mother Nature

-it is NOT man made!

• An inorganic material

(It is NOT and has

NEVER been living)

It is NOT a liquid

It is NOT a gas

It is a SOLID

It has a crystalline structure when examined under a microscope

It has either a • cubic

• hexagonal• orthorhombic

• monoclinic• triclinic

or• tetragonal

Crystalline Structure

It has a definite chemical composition

• Every atom of the mineral has the same chemical formula

• For example: Halite: NaCl Galena: PbS

Fluorite: CaF2

Talc: Mg3Si4O10(OH)2

A mineral is:

• naturally occurring

• inorganic

• solid

• crystalline structure

• chemical composition

• Now

• I

• See

• Crystal

• Clear.

Classification of minerals

HARDNESS

• Geologists use the Mohs Hardness Scale to determine a mineral’s hardness.

• The Mohs Hardness Scale ranks a mineral’s hardness from 1-10 with 1 being the softest ( can scratch it with your fingernail) and 10 being the hardest (cannot be scratched by any other substance).

• The mineral with a Mohs Hardness Scale of 1 is talc.• The mineral with a Mohs Hardness Scale of 10 is

diamond.

Color

• Color is a physical property of a mineral.

• It is NOT a dependable way to classify minerals because many minerals may have the same color.

Examples:• Gold and pyrite are both gold.• Quartz may be rosy pink, white, purple, gray or

yellowy.

Streak

• A mineral’s streak is the color it leaves behind when scratched on an unglazed tile called a streak plate.

• A mineral’s streak is the color of its powder.

Luster

• A mineral’s luster describes how the mineral reflects light.

Examples:

• Minerals that are metals are shiny.

• Quartz has a glassy luster.

• Talc has a greasy luster.

Density

• Each mineral has its own characteristic density. That is why density is an excellent way to identify a mineral.

• Density refers to a mineral’s mass per unit of volume.• Geologists use a balance to determine a mineral’s mass

and water displacement with a graduated cylinder to determine its volume.

• Density is expressed in units called grams per cubic centimeter.

• The formula for calculating the density of a mineral (or any substance) is its mass divided by its volume.

Cleavage and Fracture• Cleavage refers to a mineral’s ability to

split along flat surfaces. (String cheese has cleavage along a regular surface.)

• Fracture refers to a mineral’s ability to break along irregular surfaces. (Tearing a piece of paper is an example of what this looks like.)

Special Properties

• Some minerals have magnetic properties. That means that they are attracted to magnets.

• Some minerals are fluorescent. That means that they glow under ultra violet (UV) light.

• Some minerals are radioactive. They cause a Geiger counter to be set off.

• Other minerals have electrical properties. Quartz produces a slight electrical current when pressure is applied to it.