MINERALSThey’re not only in your breakfast cereal.

What is a mineral?

• A mineral is typically a compound consisting of more than one element.Ex. Halite (NaCl)

• There are minerals that consist of only one element. Ex. Graphite (C)

Characteristics of a mineral• Naturally occurring

• Inorganic

• Solid

• Has a definite chemical composition.

• Has a crystalline structure. (an orderly internal arrangement of atoms.

A crystal is composed of a structural unit that is repeated in three dimensions. This is the basic structural unit of a crystal of

sodium chloride, the mineral halite.

Minerals have distinctive physical and chemical

properties that allow for their identification.

Hardness• Resistance to

being scratched.

• Controlled by the strength of bonds between atoms

• Comparative identification with Moh’s scale.

Cleavage

• The tendency of a mineral to break along zones of weakness to form smooth planes.

Fracture

• A mineral that lacks zones of weakness will exhibit uneven breaking surfaces.

Streak• Color of a mineral when it is powdered

• This characteristic is usually very consistent.

Luster

• The way a mineral’s surface reflects light

• Two groups: metallic and non-metallic.

Color

• The most obvious but often the least useful.

• Because:

• The same mineral can be different colors.

• Different minerals can be the same color.

Special Properties of Minerals Carbonates react with

dilute HCl and other acids by fizzing or bubbling (releasing CO2 gas)

Special Characteristics - Fluorescence

• Some minerals will glow when placed under short-wave or long-wave ultraviolet rays

• Franklin and Ogdensburg NJ are famous for their fluorescent minerals

Special Characteristics -Salty Taste

• DO NOT TASTE MOST MINERALS!

• Halite is the exception - it will taste salty

The Crystal Cave of Giants was accidentally discovered in 2000 by miners working in the silver and lead mine at Naica, Mexico. It lies almost 300 meters (900 feet) below the surface of the Earth and it contains the largest crystals known in the world

Special Characteristics -Magnetism

• Many iron minerals will produce an invisible magnetic force field

• “Lodestone” was used by Vikings more than 1,000 years ago as compasses