Transcript Definition of a mineral

The Wild, Wacky World of Minerals
Group Activity:
Classification
1. Observation of minerals
2. Group all minerals into three categories.
3. Explain why you chose these categories
and how the minerals fit them.
Minerals: Building Blocks of Rocks
- Definition of a mineral:
•Naturally
occurring
•Inorganic solid
•Ordered internal
molecular structure
•Definite chemical
composition
- Definition of a rock:
•A solid aggregate
or mass of minerals
OK, so a mineral makes a rock.
But, what makes a mineral?
Elements!
Elements make minerals,
and atoms make elements!
- Elements
- Atoms
•Basic building blocks of
minerals
•Smallest particles of
matter
•Over 100 are known (92
naturally occurring)
•Retain all the
characteristics of an
element
Quick Recap!
Atoms make
Minerals,
which make
Elements,
which make
Rocks!
Physical Properties of Minerals
Optical Properties
- Luster
Shape Properties
-Crystal shape or habit
-Ability to transmit light
- Color
- Streak
“Other” Properties
- Taste/Smell
Weight/Mass Properties
- Density
- Specific Gravity
Strength Properties
- Texture
- Tenacity
- Glow in the dark
- Hardness
-Acid reaction
- Cleavage
- Magnetic
- Fracture
Optical Properties
-Luster: The appearance or quality of light reflected from the surface of a mineral.
Minerals with the appearance of metal are said to have a “metallic luster.” Other
non-metal-like minerals have a nonmetallic luster, and are also known as
vitreous/glassy, dull/earthy, pearly (like a pearl), silky (like a satin sheet), or
greasy (as though covered in oil).
-Ability to transmit light: Can light shine through the mineral? If so, it might be
considered transparent. If not, it could be called opaque. If light can shine
through the mineral but not an image, it is called translucent.
-Color: Easiest property to spot; worst property to use in interpreting a mineral.
Lots of minerals have the same color!
- Streak: The color of the powered mineral. Useful when you have several
different colors of the same mineral. The streak will always be the same for a type
of mineral.
Examples of Optical Properties
-Luster:
Metallic
Metallic
Non-Metallic
Earthy/Dull
-Ability to transmit light:
Opaque
Translucent
Transparent
Pearly
Glassy
Examples of Optical Properties
- Color:
- Streak:
Shape Properties
- Crystal shape or habit: This refers to the common or characteristic shape of a
crystal or aggregate of crystals. Some minerals tend to grow equally in three
directions, while others tend to be elongated in one direction. Commonly used
terms to describe these and other crystal habits include equi-dimensional, bladed,
fibrous, tabular, prismatic, platy, blocky, and botryodial.
Pyrite has two or more
characteristic habits
Weight/Mass Properties
-Density: Density is an important property of matter defined as mass per unit
volume, usually expressed as g/cm3.
- Specific Gravity: Mineralogists use a related measure to density, called specific
gravity, to represent the ratio of a mineral’s weight to the weight of an equal
volume of water. With a little practice, you can estimate specific gravity by
holding a mineral in your hand. If it feels about as “heavy” as similar-sized rocks
you have held, the specific gravity of the sample will likely be between 2.5 and 3.
Quartz, a common rock-forming
mineral, has a specific gravity of 2.65.
Galena, a which is a metallic mineral and
an ore of lead , has a specific gravity of 7.5.
Strength Properties
-Tenacity: This describes a mineral’s toughness, or its resistance to breaking or
deforming. Minerals that are ionically bonded, such as fluorite and halite, tend
to be brittle and shatter into small pieces when struck. Minerals with metallic
bonds, such as copper, are malleable, or easily hammered into different shapes.
-Hardness: One of the most useful diagnostic properties of minerals! This is
the measure of the resistance of a mineral to abrasion or scratching. This
property is determined by rubbing a mineral of unknown hardness against one
of known hardness. A numerical value of hardness can be obtained by using
the Mohs scale.
-Cleavage: This describes the tendency of a mineral to break (cleave) along
planes of weaker bonding.
- Fracture: Minerals having chemical bonds that are equally, or nearly equally,
strong in all directions exhibit a property called fracture. When minerals
fracture, most produce irregular surfaces.
Examples of Strength Properties
-Tenacity:
Brittle
Malleable
Sectile
Elastic
-Hardness:
Examples of Strength Properties
-Cleavage:
Where a mineral’s bonds will
want to naturally break (kind of
like cake layers).
Examples of Strength Properties
-Fracture:
A description of a mineral whose bonds
are equally, or nearly equally strong in
all directions, causing it to break
unevenly (like a loaf of bread).
The above is an example of
conchoidal fracture. The
smooth curved surfaces result
when minerals break in a
glasslike manner.
“Other” Properties
-Taste/Smell: Halite, which is ordinary salt, can be quickly identified
through taste. Sulfur smells like rotten eggs, and is easily identified by
smell.
-Texture: Talc and graphite have very distinctive feels. Talc feels soapy,
and graphite feels greasy.
-Glow in the dark: Some minerals have a chemical composition that
allow them to take on a fluorescent glow.
-Acid reaction: Certain minerals, called carbonates, will effervesce (fizz)
as carbon dioxide gas is released. You can see the reaction by placing a
drop of dilute hydrochloric acid on the mineral.
- Magnetic: A few minerals have a high iron content and can be picked
up with a magnet.
Mineral Project!
Due Monday, Sept. 19
Also for Monday: Read Chapter 2