Pre Lab 4 -Identification of Minerals
pdf
keyboard_arrow_up
School
CUNY College of Staten Island *
*We aren’t endorsed by this school
Course
101
Subject
Geology
Date
Dec 6, 2023
Type
Pages
4
Uploaded by ProfessorMetalEchidna20
Name: -----------------------------
Date: ----------------
---
Lab 4 Minerals
Pre-lab reading and Quiz
Read Chapter 3 of “Earth Science” and review your lecture notes on minerals.
In order to identify minerals, geologists describe a selection of physical properties that, when
used together, define each of the common minerals.
Color
: This is the color you see when you look at the mineral. Be specific i.e. say “red, brown
and yellow” rather than “multicolored” or “various”. Also distinguish between white and clear.
This may be different to another sample of the same mineral.
Streak
: This is the color of the mineral when it is powdered. To test for this color, you draw the
mineral across the surface of a piece of white porcelain, called a
streak plate
. The mark the
mineral leaves on the surface shows the color of its streak. This color is much less variable than
the general color you see when looking at the whole mineral. If a mineral is harder than the
streak plate, it will not powder. Be careful to differentiate between a mineral with no streak
(because it’s too hard) and one with a white streak.
Luster
: This is a property of the mineral’s surface, and is independent from its color. It describes
how the mineral surface reflects light. Two sample of the same mineral may have a different
luster.
Metallic – mineral appears shiny like a new coin Vitreous
– mineral looks glassy
Resinous – mineral surface looks like resin or plastic
Pearly – mineral surface looks like a pearl or the inside of a seashell Dull –
mineral reflects little light and looks like dirt or soil
Greasy – mineral surface has a greasy look and feel
Hardness
: This is a measure of how resistant a
mineral is to abrasion, and is measured on a scale
called Mohs scale. The hardest mineral is diamond,
with a hardness of 10, and the softest is
talc, with a hardness of 1. Harness is measured by
Mineral
Hardness
Talc
1
Gypsum
2
Calcite
3
Fluorite
4
Apatite
5
Orthoclase
6
Quartz
7
Topaz
8
Corundum
9
Diamond
10
Jessica
Hart
1
testing whether a mineral may be scratched by another
mineral of known hardness (see table on right), or by
another object of known hardness. In the lab you will be
testing minerals with your fingernail (hardness 2.5), a
copper penny (hardness 3.5) and a glass plate (hardness
5.5). You will therefore be able to define hardness as <
2.5, 2.5 – 3.5, 3.5 – 5.5 or > 5.5.
Cleavage and fracture
: There are two different ways that a mineral may break. If it breaks
along an irregular surface, the mineral is described as having
fracture
. However, if it breaks
along a flat surface, parallel to one of the faces of the crystal, then it is described as having
cleavage
. Such cleavage planes are related to the chemical structure of the crystal. The angles
between cleavage planes are often unique to a particular type of mineral, making them a good
guide to identification.
Effervescence
: A mineral may react (fizz) when a drop of weak hydrochloric acid is placed on its
surface.
Habit
: Characteristic form in which the mineral grows. Related to crystal structure.
Pre-Lab Qui
z
1. What would you use a streak plate for?
2. How soft does a mineral have to be for you to scratch it with your fingernail?
To
test
minerals
2.5
or
less
3. How hard does a mineral have to be for it to scratch a glass plate?
4. Describe the difference between cleavage and fracture.
5. Why is the color not always useful for identifying the mineral?
6. What do brown Hematite and black Hematite have in common?
7. What is the difference between Graphite and Diamond?
8. What is Mohs scale of hardness?
greater
than
5.5
cleavase
is
the
way
minerals
break
along
flat
planes
Fracture
breaks
in
random
Pattern.
color
is
a
variable.
you
can
scratch
both
with
a
fingernail
They
have
different
crystal
Structures
and
bonding
arrangements
A
scale
of
hardness
for
minerals
that
range
from
-10
based
on
the
ability
of
a
hardermaterial
to
scratch
a
softer
material
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
3. How hard does a mineral have to be for it to scratch a glass plate?
4. Describe the difference between cleavage and fracture.
5. Why is the color not always useful for identifying the mineral?
6. What do brown Hematite and black Hematite have in common?
7. What is the difference between Graphite and Diamond?
8. What is Mohs scale of hardness?
it