Minerals identification 4 1

Section 1: Properties of
Minerals


What is a mineral?
How are minerals identified?


 mineral – A naturally occurring, inorganic solid that has a crystal
structure and a definite chemical composition.

 A substance must have all 5 characteristics to be classified as a
mineral.


A mineral must be/have:
 Naturally Occurring

 Inorganic
 Solid
 Crystal Structure
 Definite Chemical Composition


The substance must be formed

by processes that occur naturally
in the world
Example: quartz
Forms naturally when magma
cools and hardens deep beneath

the Earth’s surface.


 Materials such as cement, plastic, brick, steel, and
glass all come from substances found in Earth’s

crust but they are manufactured by people.


 Inorganic – the mineral cannot arise from materials
that were once part of a living thing

 Ex. Coal is NOT a mineral because it is made up the
remains of plants and animals




A mineral is always solid



Has a definite volume and shape.



Particles that make up a solid are tightly packed together, therefore they move very little
(compared to the particles of a liquid)

 Particles of the mineral line up in a pattern that repeats.
 The repeating pattern of the minerals particles forms a solid
called a crystal

 Faces – are flats sides of the crystal

that meet at sharp edges and
corners


 Element – a substance composed of a single kind of atom.

 Ex. Hydrogen
 Compound – Two or more elements combined so that the
elements no longer have distinct properties

 Ex. Water H20


 Minerals always contain certain elements in definite proportions; most
minerals are compounds

example: Quartz
SiO
2
One element of silicon, 2 elements of oxygen
 Compounds have their own unique properties that differ from the
properties of the elements that form it.

 Some elements that occur in nature, in pure form, that are
minerals include:

 Gold (Au), Silver (Ag), Copper

(Cu)
 Listed on the periodic table


 Geologists have identified about 3,800 minerals
 Each mineral has characteristic properties that can be used to
identify it.

 Some properties can be determined by looking at it, some
properties require testing.


 Color
 Streak
 Luster
 Density
 Hardness

 Crystal Systems
 Cleavage and fracture
 Special Properties


 An easily observed physical property.
 Color alone is not enough to make an identification.



Ex. Gold, pyrite and chalcopyrite = gold
color

 Only a few minerals can be identified using color only.



Ex. Malachite- always green, azurite –
always blue.


 The streak of a mineral is the color of its powder
 The streak color and the mineral color are often different
 To test: rub a mineral against an unglazed tile (streak plate)


 Luster – used to describe how a mineral reflects light from
its surface.

 Minerals containing metals are often shiny.
 Other terms to describe luster - Earthy, waxy, and pearly.



 Each mineral has a characteristic Density.
 Density – the mass in a given space or mass per unit volume.
 Density = mass (g)

volume (cm3)

 Displacement – the volume of the displaced water equals the
volume of the sample


- Properties of Minerals

 To calculate the density of a mineral, divide the mass of the mineral
sample by its volume.

 Density = Mass/Volume
 For example, if a sample of olivine has a mass of 237 g and a volume
of 72 cm3, then the density is

 237 g/72 cm3 = 3.3 g/cm3




Take a few minutes to work through the following problem with a partner.


A sample of calcite has a mass of 324 g and a volume of 120 cm3. What is its density?


324 g ÷ 120 cm3 = 2.7 g/cm3



Take a few minutes to work through the following problem with a partner.


- Properties of Minerals



Predicting:

A piece of pyrite has a
volume of 40 cm3. What is
its mass?