Minerals

What is a mineral? Mineral is a naturally occurring solid

composed of several different elements.

Most rocks are aggregates composed of two or more minerals.

Each mineral has its own unique characteristics.

A mineral is the same all the way through.

What makes up a mineral?• Different minerals are made up

of different elements.• The elements include:

– silicon – oxygen – iron – sodium – chlorine – calcium – carbon – hydrogen – aluminum

What are the unique properties of minerals?

• Each mineral has unique properties.– Crystal Forms– Luster – Hardness – Streak – Acid Reaction – Fluorescence

Crystals• Crystals are structures made up of

a regular repeated pattern of connected atoms or molecules.

• There are many different forms of crystal.– Cubes, spheres, pyramids, spikes,

and some are even 12 sided (like a die)

• Each mineral has a specific crystal form.

Luster• Luster is the quality or

appearance of light reflected.• There is metallic luster and

nonmetallic luster.• Metallic luster:

– Reflects light like metal.– Silver and gold have metallic

luster.

• Nonmetallic luster:– Includes silky, glassy, pearly, and

dull.– Quartz has nonmetallic luster.

Luster

Hardness• Hardness is the resistance to

scratching or abrasion.• This is the most useful

characteristic of minerals. • Each mineral has a specific

hardness.• There is a scale called “Mohs

Scale”. – It lists ten minerals in order of

their hardness.

Hardness• Mohs scale consists of ten

minerals that you can use as a reference.– Talc is the softest and diamond is

the hardest.– Talc has a hardness of 1, diamond

has a hardness of 10.

Mohs Hardness Scale

1 2 3

Talc Gypsum Calcite

4 5 6

Fluorite Apatite Feldspar

7 8 9

Quartz Topaz Corundum

10

Diamond

Mohs Hardness Scale• To use the hardness scale, try

to scratch the surface of an unknown sample with a mineral or substance from the hardness scale (these are known samples).

• If the unknown sample cannot be scratched by feldspar (6) but it can be scratched by quartz (7), then it's hardness is between 6 and 7.

• An example of a mineral that has a hardness between 6 and 7 is pyrite (6 to 6.5).

Hardness•If the minerals on the hardness scale are not accessible, use common household items.•So if there was an unknown mineral that could be scratched by the knife but could not be scratched by the glass, then the hardness would be between 5.5 and 6.5.

Common Objects and Their Hardness Values

2.5 3.5 5.5 6.5 8.5

Fingernail Penny Glass Steel knifeEmery cloth

Streak• When a mineral is rubbed firmly

across an unglazed tile of white porcelain (a streak plate), it leaves a line of powder.

• This is called the streak. • The color of the streak is always

the same, whether or not the mineral has impurities.

• For example, quartz leaves a white streak, whether it's violet (amethyst), pink (rose quartz), or brown (smoky quartz).

Streak

Acid Reaction• Some minerals contain

elements that react with acids to produce gases.

• The carbonate minerals have this reaction.– Carbonate minerals are minerals

that contain carbon.– Calcite is an example of a

carbonate mineral.

Florescence• Florescence is whether or not

the mineral glows under a black light.

• The fluorescent minerals are minerals that emit visible light when activated by invisible ultraviolet light (UV), X-rays and/or electron beams

• Activator elements are responsible for fluorescence. But not all specimens have these activator elements.

Florescence

Florescent Calcite

Florescent Gypsum

Review

• What is a mineral?• What are six characteristics

that can be used to identify minerals?

• What is luster?• What is hardness? • What are crystals?• What is streak?• What is fluorescence?

Copyright Information

• All information was retrieved from research done on the internet in February 2007.

• All pictures were retrieved from a Yahoo image search in February 2007.