Name: Wong Jun Yan Johnson

UID: 3035466681 CIVL2102 Laboratory Report (Mineral)

THE UNIVERSITY OF HONG KONG

DEPARTMENT OF CIVIL ENGINEERING

CIVL2102 Engineering Geology and Rock Mechanics

Laboratory Report
Identification of Minerals and Rock Slice Observation Experiment

Name: Wong Jun Yan Johnson

University Number: 3035466681
Subclass Group: C

1
Name: Wong Jun Yan Johnson
UID: 3035466681 CIVL2102 Laboratory Report (Mineral)

Contents
 Identification of Minerals………………………………………………..………3
 Introduction and Objectives………………………..………………….…….3
 Equipment…………………………………………………………….…….3
 Methodology………………………………………………………….…….4
 Procedures…………………………………………………………….…….4
 Results - Mineral Identification in Hand Specimens……..……………....….5
 Discussion - Properties and Characteristics of Minerals…….…..………..…7
 Discussion – Further Analysis and Identification of Minerals…....................8
 Discussion - Possible Source of Errors and Limitations………….………13
 Conclusion……………………………………………………………….13
 Rock Slice Observation Experiment…………………………………………….14
 Introduction and Objectives………………………..………………………14
 Equipment…………………………………………………………………14
 Methodology and Procedures………………………………………...……14
 Rock Slice Details………………………………………………….………14
 Results - Mineral Composition….…………………………………………15
 Discussion – Analysis and Comparison of Results………………………16
 Discussion - Possible Source of Errors and Limitations…….……………...16
 Conclusion…………………………………………………………………17

2
Name: Wong Jun Yan Johnson
UID: 3035466681 CIVL2102 Laboratory Report (Mineral)

Identification of Minerals
Introduction and Objectives
Mineral is a naturally occurring chemical compound. Different minerals have different
physical properties, chemical properties and characteristics as their chemical structure
and composition are different. In order to distinguish different minerals provided, these
minerals are identified from their morphology and physical properties. The properties
include:
 Form (Crystal or Aggregate)
 Number of cleavage directions and cleavage angles
 Shape of crystal specimen
 Streak
 Lustre
 Hardness
Based on the aforementioned properties, different minerals can be distinguished.

Equipment
Different equipment are used to discover the properties of various minerals so as to
differentiate and identify different minerals.
 Mohs’ scale of hardness box – A collection of nine minerals number 1 to 9 in order
of increasing hardness

Figure 1: Mohs’ scale of hardness box used in laboratory

 Porcelain streak plate

Figure 2: Porcelain streak plate used in laboratory

3
Name: Wong Jun Yan Johnson
UID: 3035466681 CIVL2102 Laboratory Report (Mineral)

 Pocket knife
 Magnet

Methodology
Regarding the properties of minerals mentioned in the part of Objective, the methods
of testing and discovering various properties are ascribed below.
 Form (Crystal or Aggregate)
By observation.
 Number of cleavage directions and cleavage angles
By observation of the surface and reflection of mineral.
 Shape of crystal specimen
By observation.
 Streak
Scratch the porcelain streak plate with the testing mineral. There will be a scratch
on the surface of the plate. Observe the colour of the scratch.
 Lustre
By observation.
 Hardness
Mohs’ scale of hardness box is used. The box contains nine minerals number 1 to
9 in order of increasing hardness. The principles are stated below.
 If a mineral scratches the testing mineral and there is a mark left on the testing
mineral (but no mark on the mineral), the mineral has a higher hardness than
the testing mineral.
 If a mineral scratches the testing mineral and both the mineral and testing
mineral has no marks on itself, the hardness of them should be same or very
close to each other.
At the meantime, other equipment can be used to determine the hardness. For
instance, pocket knife used in laboratory has a hardness of about 5. Hence, by these
principles and methods the hardness of a mineral can be roughly determined.

Indeed, there are still other properties that can be used to identify minerals. For instance,
magnetism can be detected by placing a magnet near the mineral. If the mineral is rich
in iron component, it can be attracted. In addition, chemical properties can be found out
For example, acidic solution can dissolve calcite as calcite is rich in calcium carbonate.

Procedures
Determine systematically the physical properties and the crystal form, or the form of a
crystal aggregate of a mineral, as following:

4
Name: Wong Jun Yan Johnson
UID: 3035466681 CIVL2102 Laboratory Report (Mineral)

1. Decide whether the mineral occurs in single crystals or in an aggregate of imperfect

crystals.
2. Determine its colour, streak and cleavage.
3. Determine whether it has a metallic or non-metallic luster.
4. Determine the hardness.

Results - Mineral Identification in Hand Specimens

1. Your mineral specimens may be in the form of a single crystal or part of a crystal or
an aggregate with more than one crystal. Complete the following table using ticks.

Specimen Number Crystal Aggregate

M4 ✓
M5 ✓
M10 ✓
M12 ✓
M14 ✓
M19 ✓
2. You are provided with six minerals with well-developed or perfect cleavages in one
or more directions. Identify the number of cleavage directions in each. (Note: Please
take special care not to damage any of the specimens)
Cleavage angle if 2 or
Specimen Number Number of cleavage directions
more directions
M8 4 90°
M9 3 75°
M10 1 /
M12 2 90°
M17 2 120°

3. Select the most appropriate term out of the following list to describe the shape of the
crystal specimens.

Massive Granular Prismatic Fibrous Rhombohedral/Diamond Platy

Specimen Number Crystal Shape

M4 Massive
M9 Rhombohedral/Diamond
M10 Fibrous

5
Name: Wong Jun Yan Johnson
UID: 3035466681 CIVL2102 Laboratory Report (Mineral)

M11 Prismatic
M14 Platy
M19 Granular

4. Streak is the colour of a mineral in powdered form. Identify the streak of the
specimens in the table.

Specimen Number Streak

M1 Grey
M2 Brown
M3 Brown
M4 Grey
M5 Reddish Brown
M18 White

5. Lustre is a term for the overall surface appearance of a mineral. There are two main
types – metallic (shiny like metals) and non-metallic e.g. vitreous or glassy, earthy or
dull. Complete the following table using ticks and supplement some more details (e.g.
appearance color & reflecting)

Non-metallic
Specimen Number Metallic
Vitreous/Glassy Earthy

M3 ✓ (grey)
M5 ✓ (grey)
M6 ✓ (black)
M11 ✓ (translucent)
M14 ✓ (dark brown)
M16 ✓ (white)

6. Determine the hardness using the hardness box provided and complete the following
table.

Specimen Number Mohs’ scale of hardness (if possible to nearest 1/2)

M4 4
M9 3
M10 2
M11 7
M13 6
6
Name: Wong Jun Yan Johnson
UID: 3035466681 CIVL2102 Laboratory Report (Mineral)

Discussion – Properties and Characteristics of Minerals

Figure 3: The collection of specimens of 20 common minerals in laboratory

The above figure shows different minerals. In light of the aforementioned properties,
we can distinguish and classify different minerals. The properties and characteristics
used will be discussed in detail below.
The first step is to find out the form of mineral – whether it is in form of crystal or
aggregate. The arrangement of materials in specimen affects the form of mineral.

Next, cleavage of different minerals is investigated. Cleavage is the tendency of mineral

to split along definite crystallographic structural planes. In other words, it refers to the
way of mineral break along certain lines of weakness in its structure. In different
minerals, the cleavage planes will be different and different minerals have different
cleavage angles.

After that, shape of the crystal specimens is discussed. Different minerals have various
geometric shapes formed in the environment and it is governed by mineral’s internal
structures. Different terms are used to describe the shape of it:
For the form of aggregate:
 Massive: Indiscernible crystals are too fine to observe
 Granular: Aggregates of anhedral crystals in matrix
For the form of crystal:
 Prismatic: Well-developed crystal faces parallel to the vertical axis
 Fibrous: Fiber-like structures bonded together
 Rhombohedral/Diamond: Cube-liked structure
 Platy: Flat, tablet-shaped

Next, streak refers to the color of the mineral in powdered form. Streak is different from
the color of the mineral. The powder of the mineral has a more consistent characteristic
color, thus being crucial in mineral identification.

7
 Name: Wong Jun Yan Johnson
UID: 3035466681 CIVL2102 Laboratory Report (Mineral)

Moreover, lustre is used to describe the overall surface appearance of mineral. Lustre
refers to the way that mineral reflects light. Minerals can be classified as metallic or
non-metallic based on their appearance. Metallic means shiny as metal under light. On
the other hand, non-metallic minerals can be distinguished as vitreous/glassy or earthy.
Earthy is used to describe minerals with a dull reflective surface.

Finally, hardness of different minerals is tested. Hardness is controlled by the strength

of bonds between atoms and is measured by the ease or difficulty with which it can be
scratched. In other words, hardness refers to the resistance of the mineral to scratching.
Fingernail has a hardness of about 3. Mohs’ scale of hardness is introduced to test and
compare the hardness of different minerals.

Discussion – Further Analysis and Identification of Minerals

In order to distinguish and classify various minerals, different properties and
characteristics are observed and compared. Carrying out the comparison more clearly
and systematically, the below table provides the photo and the characteristics of
corresponding minerals. Besides summarizing some of the observable findings above,
additional unique properties may be stated so as to identify different minerals clearly.

Specimen Mineral
Photo Characteristics
Number Name

 Metallic luster and

pale brass-yellow hue
M01 Pyrite  Appearance similar to
gold
 It has a grey streak

 It appears black and

dark as the iron content
is high
M02 Sphalerite
 The appearance is dull
or shiny
 It has a brown streak

8
Name: Wong Jun Yan Johnson
UID: 3035466681 CIVL2102 Laboratory Report (Mineral)

 Metallic appearance
 Brown or reddish
M03 Galena
brown in colour
 It has a brown streak

 Grey in colour and it is

in the form of
aggregate
M04 Chlcopyrite
 The shape of crystal is
massive
 It has a grey streak

 Reddish Brown in
colour and it is in the
form of aggregate
M05 Hematite  It has a metallic
appearance
 It has a reddish brown
streak

 Grey in colour and it

has a metallic
appearance
 As it is oxide of iron, it
M06 Magnetite
is strongly magnetic
and can be easily
attracted by iron
 It has a black streak

 Brown or reddish
brwon in colour
M07 Geothite  Forms prismatic
needle-like crystals
 It has a brown streak

9
Name: Wong Jun Yan Johnson
UID: 3035466681 CIVL2102 Laboratory Report (Mineral)

 Greenish colour in
light of the impurities
 It has four cleavage
M08 Fluorite
directions and
cleavage angle is 90°
 It has a white streak

 Reacts vigorously with

acid as it is a carbonate
mineral
 It is white in colour
M09 Calcite and it has a
rhombohedral shape
 It has three cleavage
directions and
cleavage angle is 60°
 Soft sulfate mineral
 It has a fibrous shape
and it is in the form of
crystal
M10 Gypsum
 It has one cleavage
direction only
 Moderately soluble in
water

 Colourless and
translucent
 It has a prismatic shape
M11 Quartz
and it has a vitreous
appearance
 It has a white streak

10
Name: Wong Jun Yan Johnson
UID: 3035466681 CIVL2102 Laboratory Report (Mineral)

 Grey or white in colour

and it is in the form of
crystal
M12 K-Feldspar
 It has two cleavage
directions and the
cleavage angle is 90°

 Reddish white or
bluish white in colour
M13 Plagioclase
 Quite brittle
 It has a white streak

 Black or dark brown in

colour
 It has a vitreous
appearance and the
M14 Biotite
shape of it is platy
 It is in the form of
crystal
 It has a white streak

 Grey or dark grey in

colour
 Consists of thin sheets
M15 Muscovite
 It is elastic when
deformed or broken
 It has a white streak

 White in colour
 It has an earthy
M16 Kaolinite
appearance
 It has a white streak

11
Name: Wong Jun Yan Johnson
UID: 3035466681 CIVL2102 Laboratory Report (Mineral)

 Black or dark brown in

colour
M17 Hornblende  It has two cleavage
directions and the
cleavage angle is 120°

 Colour is in brown or
M18 Pyroxene reddish brown
 The streak is white

 It may seem to be
reddish in colour due
to the oxidation of iron
M19 Olivine  It has a shape of
granular
 It is in the form of
aggregate

 White or pale grey in

colour
 It has a vitreous
M20 Chlorite
appearance and it has
only one cleavage
direction

As there is a myriad of properties and characteristics for different minerals, only some
of the obvious and unique characteristics are discussed in the aforementioned table.

12
Name: Wong Jun Yan Johnson
UID: 3035466681 CIVL2102 Laboratory Report (Mineral)

Discussion - Possible Source of Errors and Limitations

 The cleavage angles may be difficult to find out exactly. The accuracy may be low
because of simple observation.
 In the test of hardness, the scratching action may cause a mark to exist in the
mineral, but it may not be notified as sometimes the mark is too small and thin.
 Accurate hardness cannot be discovered and compared as the usage of Mohs’ scale
is just a rough comparison of hardness between different materials.

Conclusion
Through different tests and comparisons, the minerals can be compared and classified.
The findings are mentioned above with respect to various objectives and properties of
minerals. In addition, the details of each properties, possible source of errors and
limitations are discussed.

To sum up again, the table below shows the mineral names of different specimen
numbers identified.
Specimen Number Mineral Name Specimen Number Mineral Name
M01 Pyrite M11 Quartz
M02 Sphalerite M12 K-Feldspar
M03 Galena M13 Plagioclase
M04 Chlcopyrite M14 Biotite
M05 Hematite M15 Muscovite
M06 Magnetite M16 Kaolinite
M07 Geothite M17 Hornblende
M08 Fluorite M18 Pyroxene
M09 Calcite M19 Olivine
M10 Gypsum M20 Chlorite

13
Name: Wong Jun Yan Johnson
UID: 3035466681 CIVL2102 Laboratory Report (Mineral)

Identification of Rock Mineral Slices

Introduction and Objectives
Basically, mineral is any naturally-occurring, homogeneous solid that has a definite
chemical composition and a distinctive internal crystal structure. In other words,
mineral is the basic unit of rock as different minerals combine to form rock. Therefore,
rocks can be distinguished from minerals by their heterogeneous composition of
different minerals. In this part, a rock slice is examined in order to:
 Identify the types of minerals in a rock slice
 Determine the composition of different minerals in the rock slice
 Determine the type and name of the rock

Equipment
 Polarized light microscopy (Leica DM 750P)
 Computer (connected to the microscopy)

Methodology and Procedures

As different minerals bend light in different ways, the types of minerals can be
identified by the usage of polarized light microscopy.
1. Place the rock slide on the stage of microscopy
2. Adjust the focus and light intensive
3. Pick a region by rotating the pins
4. Capture the image using the software in computer (connected to the microscopy)

Rock Slice Details

Figure 4: Rock slice to be examined

Location: Tiu Keng Leng
Type of specimen: CH2 – Granite
Depth: 21.72-22.42m

14
 Name: Wong Jun Yan Johnson
UID: 3035466681 CIVL2102 Laboratory Report (Mineral)

Results - Mineral Composition

By box counting method, the mineral composition can be determined.

Biotite

Feldspar

Quartz

Figure 5: Polarized light microscopy image of granite sample

Figure 6: Polarized light microscopy image of granite sample with grid lines

Total number of boxes: 20 × 15 (Columns × Rows) = 300 boxes

15
Name: Wong Jun Yan Johnson
UID: 3035466681 CIVL2102 Laboratory Report (Mineral)

Type of Colour of Number of Percentage

Image(s)
mineral(s) mineral(s) boxes filled composition
68
× 100%
Quartz White 68 300
= 22.7%
186
Grey / Light × 100%
Feldspar 186 300
Brown
= 62%
Biotite Reddish Brown / 46
× 100%
/Hornblende/ Dark / Greenish 46 300
Olivine yellow = 15.3%
(The numbers are corrected to 3 significant figures if necessary)

Discussion – Analysis and Comparison of Results

As mentioned above, the rock slice of granite, which is an intrusive igneous rock, is
examined. The theoretical composition of minerals in granite should be:
Types of minerals Theoretical percentage composition
Quartz ~ 30 % (20% - 40%)
Feldspar ~ 55% (50% - 70%)
Biotite / Hornblende / Olivine ~ 15%

In the above experiment, the percentage composition of minerals found in the granite
slice is discovered. The composition of mineral in granite sample found is:
Types of minerals Found percentage composition
Quartz 22.7%
Feldspar 62%
Biotite / Hornblende / Olivine 15.3%

Comparing the theoretical composition and found composition of minerals in granite,

the found composition of minerals is close and similar to the theoretical composition.

Discussion - Possible Source of Errors and Limitations

 Through the observation of rock slice by virtue of polarized light microscopy,
different parts or sections of the rock slice have different mineral contents. In other
words, the minerals are not evenly distributed and different parts have different
mineral composition. This causes variations in observation and judgement of
mineral content.

16
Name: Wong Jun Yan Johnson
UID: 3035466681 CIVL2102 Laboratory Report (Mineral)

 The usage of box counting method is not accurate and precise enough to determine
the exact mineral content of rock. It is just a rough judgement.
 The light intensity of microscopy may affect the judgement of different minerals.

Conclusion
In this laboratory session, the mineral composition of rock slice is analyzed by the usage
of polarized light microscopy and box counting method of the microscopic image of
part of the rock slice. At the meantime, different source of errors and limitations are
discussed.

17