Mineral Notes

advertisement

Chapter 5

1. Inorganic

2. Occurs naturally

3. Crystalline solid

4. Consistent chemical composition

Gypsum

Fluorite

Salt?

Sugar?

Ice?

Charcoal?

Rock?

Scientists have identified 3,000 minerals

Of those minerals, there are 20 common

rock-forming minerals

All minerals are divided into 2 main groups: Silicate and Nonsilicate Minerals

Silicates

Nonsilicates

Must have Silicon and Oxygen

Usually has additional elements like Ca, Na, K,

Fe, or Mg

96% of Earth’s crust

Quartz and feldspar make up more than 50% of the crust

Do not contain silicon and oxygen

Make up 4% of Earth’s crust

There are 6 major classes

Mineralogists identify minerals based on a number of specific physical properties:

Color

Streak

Luster

Cleavage and Fracture

Hardness

Crystal Shape

Density

Easy to observe

Unreliable

Trace amounts of elements can change color

Weathering can change color

The same mineral can come in different colors.

Rubies are cut from corundum with traces of Chromium (Cr)

Sapphires are cut from corundum with traces of Cobalt (Co)

Color of the mineral in the powder form

More reliable than color

Use a

streak plate

Minerals that are harder than the streak plate will leave no streak because it is too hard to rub off on the plate

Light reflected from the mineral’s surface

Metallic luster

Nonmetallic luster

: waxy, pearly, glassy, dull/earthy, or vitrious/brilliant

Cleavage

is the tendency of a mineral to split along specific planes of weakness to form smooth, flat surfaces

Cleavage in three directions. Example: CALCITE

Fracture

is when the mineral does not split along cleavage planes

Fracture can be irregular, fibrous, or conchoidal

A measure of the ability of a mineral to resist scratching

Hardness relates to the strength of bonds between the minerals atoms (Ex:

Diamond vs.

Graphite)

To determine an unknown mineral’s hardness, you need to scratch it against a mineral of known hardness

TETRAGONAL, ORTHORHOMBIC,

HEXAGONAL, TRICLINIC, MONOCLINIC,

ISOMETRIC

Ratio of mass to volume of a substance

Density = mass/volume

Most minerals have a density between 2 and 3 g/cc

Lead

Density = 11.35 g/cc

Galena

Density = 7.6 g/cc

Fluorescence – ability to glow under UV light

Double Refraction – light is bent to produce a double image

Magnetism

Radioactivity

Download