ROCKS & MINERALS
TOPIC 11

• Minerals are the
ingredients of
rocks.
Or
• Rocks are made
up of minerals.

Minerals
• Defn: naturally occurring, inorganic
elements or compounds with specific
physical and chemical properties.

Mineral Properties
 Used to identify minerals
1. Color
• Least useful property in identifying
minerals.
• Why?

All of these are varieties of quartz!

2. Streak
• The color of a minerals powder.
• “streak test”

3. Luster
• How the minerals surface reflects
light.
• Metallic vs. non- metallic.

4. Hardness
• The ability of a mineral to resist being
scratched.
• “Scratch test”
• If mineral A can scratch mineral B, what
does that tell us about the relative
hardness of each mineral?

Moh’s Hardness Scale
Soft
Hard

5. Fracture/ Cleavage
Fracture
• Mineral breaks
unevenly or
irregularly
Cleavage
• The tendency of
a Mineral to
break evenly
along its weakest
plane.

6. Crystal Form
• Some minerals tend to form crystals that
aid in the identification of the mineral.

7. Specific Gravity
• The ratio of the density of the mineral to
the density of water (1 g/cm3)
• If a mineral has a specific gravity of 5
that means it is 5 times as dense as
water.

8. Others
• Acid test – Calcite
• Magnetic – Magnetite
• Taste - Halite

A minerals properties are
due to the internal
arrangement of its atoms.

Silicate Minerals
• Minerals that contain a combination of
silicon and oxygen.
Silicon-oxygen tetrahedron
The basic structural unit of silicate minerals

Rocks
Monomineralic
• 1 Mineral
Polymineralic
• More than 1 Mineral
 Rocks are classified by
how they are formed!!!

Sedimentary Rocks:
1. Clastics
• Rocks that form when sediments (sand,
silt etc.) are lithified.
Processes
• Compacting and cementing
• Vary due to grain size! (see ref tables p.
7)

2. Non-Clastics
A. Organics (bioclastics)
• Form from living things.
Examples: Coal, limestone
B. Chemical (crystaline)
• Formed from the evaporation or precipitation
of sea water.
Examples: Halite, gypsum

Igneous:
- Form when liquid rock cools and solidifies
Intrusive
• Cools below the
earths surface
(slowwwwly!)
• Magma
• “Plutonic”
Extrusive
• Cools at the Earths
surface (quickly!)
• Lava
• “Volcanic”

The longer the rock takes to cool, the
larger the crystals!
• Cools slow …..Large crystals
• Cools fast …….small crystals
• Cools immediately……NO Crystals (glass)

Vesicular- gas pockets

Metamorphic:
• Rocks that are changed due to extreme
heat and/or pressure.
• DO NOT MELT!!! (they recrystalize)
Metamorphic rocks become…
1. Harder
2. More dense
3. Banded or foliated
4. Distorted

Banding

Foliated

Regional Metamorphism
• Occurs when large areas of rock are
changed.
• Usually deep below the surface where
crustal plates collide.
• The Adirondacks!

Contact Metamorphism
• Occurs when liquid rock comes into
contact with other rocks.

Bedrock Of New York State

Identifying Characteristics of
Rocks
Igneous
• Intergrown crystals
• Glassy texture
Sedimentary
• Cemented fragments
(sediments)
• Fossils
• Organic material
Metamorphic
•Banding
•Foliated

The Rock Cycle

BONUS:
• CLASSIFY this rock as igneous,
sedimentary or metamorphic and
EXPLAIN why you classified it that way.

BONUS:
Name the mineral that has the following
properties:
• Non-metallic
• Can scratch fluorite but cannot scratch
quartz
• Exhibits cleavage
• Contains the elements sodium &
hydrogen