Name(s) _______________ and ____________ Section 1 2
Lab 3: Minerals – 2012 AGI Manual, 9th Ed.
There are three parts to your work on minerals. Use your lab manual (Busch and
Tasa 8 ed.) for references and guidance. You should read the text in the Manual on
p.57-80. The point of the text is to acquaint you with the different types of physical
properties which enable us to distinguish minerals: density, hardness, luster, streak,
crystal form, habit, colour etc. Also read the handouts on mineral identification properties
and use them along with the identification tables in your book and your target list of
minerals to learn for the Minerals quiz in 2-3 weeks. As you examine each of the
different minerals, practice doing the different physical properties tests to tell the
minerals apart as in the Michigan Tech video. You will have two lab periods in which to:
th
A. Work with your lab partner and use standard physical methods for testing and
identifying some common minerals. Rock identification in subsequent labs depends
first on learning how to identify common rock forming minerals.
B. Become familiar with the physical properties of common minerals. In particular, this
includes: the common “rock-forming minerals” like feldspars, micas; the rarer
“accessory minerals” like magnetite, corundum, and some economically important
“ore minerals” that supply most of our chemical, industrial and metallurgical needs.
C. The completed written exercise must be handed in by the end of the second minerals
lab. Meanwhile learn to do the tests and ensure that you are in fact getting the correct
value or answer for each mineral you examine. This will also help you build first
hand experience with distinguishing and naming the various mineral properties such
as: pearly luster, intermediate specific gravity, soft minerals, rhombohedral crystal
form, massive habit, etc.
D. Hand in one lab per pair of lab partners. You do not need to be in the lab to do some
of this part of your work. You can use the exercise to familiarize yourself with the
tables of mineral characteristics in the lab manual. You need to be very familiar with
this information before we study rocks in detail.
The mineral labs are very important. Your ability to identify and understand
rocks in later labs, depends first, on developing fundamental skills that assist one in the
identification of minerals. Time and practice is required to attain these skills.
Additionally, you should read about and learn some common uses of minerals.
Turn to lab 3 in the manual and work your way through the readings and
exercises. There are trays of minerals separated by their dominant or largest chemical
component (usually an anion type: silicate, carbonate, sulfide, oxide etc.) Minerals are
considered in a related family for either chemical composition or for sharing a common
internal crystal structure. Some of the related minerals may seem surprising until you
understand the similarities. We also have “non-destructive” sample boxes of minerals
characterized by a particular luster, cleavage, fracture or hardness. Work your way
through the questions and try to find a specimen of each mineral or property involved.
1
Activity 3.1: Mineral physical properties and uses
A. Find samples of these materials in the lab and compare their appearance in
reflected white light to learn to tell their lustre apart: (circle the correct answer) (7)
1. Copper coin:
Nonmetallic Metallic
2. Rock Crystal Quartz:
Nonmetallic Metallic
3. Albite Plagioclase Feldspar:
Nonmetallic Metallic
4. Ice:
Nonmetallic Metallic
5. Graphite:
Nonmetallic Metallic
6. Talc:
Nonmetallic Metallic
7. Mirror:
Nonmetallic Metallic
B. Compare the Streaks of the following minerals and write a description of the
appearance of this powdered substance when it has lost all crystal structure: These
minerals are in the brown boxes in the bins. (4)
1. halite (salt): ____________________________________________________
2. native sulphur: __________________________________________________
3. graphite (pencil “lead”): __________________________________________
4. hematite: ______________________________________________________
C. Crystal Form, Habit & Fracture: Compare quartz crystals in fig 3.11 A and B with
similar ones in our mineral collection trays. Name each variety, describe its crystal size &
luster. Habit is how the crystal grew (faces, geometric form or crystal shapes & sizes).
Describe this. Fracture is how it breaks, see figure 3.10. Describe this. (10)
Variety
Name Crystal Size
Lustre
Habit
Fracture
1.White opaque
2.Clear translucent
D. Find these 4 varieties of quartz in our own collection or in our display cases then
name the varieties of quartz in fig 3.1a-d: There are many different colours possible in
quartz due to either mineral or chemical impurities or crystal habit variations and defects
in the hexagonal structure. Not shown here but elsewhere in our collection you can find
green quartz called adventurine and red microcrystalline quartz called jasper. Both are
like the purple and yellow-orange ones here are semi-precious gems (4)
1. purple:_____________________________________________________
2. white:______________________________________________________
3. grey:_______________________________________________________
4. yellow banded: _______________________________________________
2
E. Hardness: Look at Moh’s hardness scale on p 63-64, Fig 3.9 and note the minerals &
common objects which enable us to test hardness (the strength and frequency of mineral
bonds). This scale is non-linear, so the harder minerals are progressively very much
harder. The division between hard and soft minerals is set between feldspar (half of most
common igneous rocks) and apatite (the mineral portion of your teeth and bones) or
above and below window glass or an iron nail. From the index minerals in Moh’s scale,
which mineral has this hardness value? Find this mineral and test it yourself. (3)
(circle one)
1. wire nail < mineral < masonry nail
HARD or SOFT
2. moh’s hardness =
______________
3. mineral name =
______________
F. Hardness: From the index minerals in Moh’s scale, which mineral has this hardness.
Find this mineral and test its hardness and other properties yourself. Be sure when you
test the hardness of a mineral to reverse the test for who is scratching who! It is easy to
do this test on a large crystal of a single mineral, but less so for massive or aggregate
specimens that tend to crumble before they scratch. If they do this, use the crumbled
pieces as a polish to see if they will leave a scratch. (3)
(circle one)
1. calcite < mineral < iron nail
HARD or SOFT
2. moh’s hardness =
______________
3. mineral name =
______________
G. Sulphide Mineral Identity: Look at the mineral pictured in figure 3.7a and 3.8. As
pictured this mineral has a distinct crystal form like one of those in Fig. 3.5. It also has a
special property of growing with striated faces. This mineral also has a metallic lustre
which readily tarnishes or rusts, a dark grey streak that stinks like rotten eggs when
reacted with acid. It also has an intermediate density/specific gravity. (8)
1. mineral (Fig 3.7a, 3.8) hardness > glass =
___________
2. name this particular crystal form/habit (F3.6a):
___________
3. name this mineral:
___________
4. chemical formula & chemical compound name: ___________
5. use (ore of):
___________
6. find a piece of this & determine it’s streak:
___________
__________
7. What is the major environmental issue for this?
________________________________________________________________
_________________________________________________________________
3
H. Carbonate Minerals: compare real samples to photos in (F3.17): Common 2+
metal cations (Ca, Mg, Fe, Mn etc.) make carbonate minerals with the abundant
water soluble carbonate (CO3)-2 anion. Because the carbonate ion is a flat
equilateral triangle, it tends to stack up in trigonal-rhombohedral crystals that form
3 perfect cleavages and crystal growth faces at about 75°/105° when you compare
interfacial angles to those on the goniometer in the back of the book (don’t tear it
out, hold the specimen up to compare). Additionally all carbonate minerals react to
acid, but most require powdering or heating and a hand lens to see the faint bubbles
of CO2 gas that are released. Since Ca+2 is so large and has a low field strength, its
carbonate reacts vigorously with cold dilute hydrochloric acid. Obtain specimens of
this common industrial mineral and put the values of your tests, observations and
other information below.
1. hardness:
____________
2. crystal form:
____________
3. mineral name:
____________
4. chemical formula & chemical name:____________
5. use (ore of/product):
____________
____________
I. Specific Gravity: A light coloured mineral has a mass of 27.0 g and displaces a
volume of water equal to 10.4 cm3 . Show your calculation and give the units for its
density, then repeat this for its specific gravity. Finally, using your mineral tables,
identify the mineral from the following choices. (6)
1.. Density =
2. Specific Gravity =
3. Mineral name (circle correct choice): Gypsum
Chalcedony Corundum
J. The following minerals are the sources of material for some common place
industrial products. Metallic minerals are termed ores if they have an economically
extractable amount of a particular metal. Other minerals are termed “industrial
minerals” when they are used to make something else like fillers in plastics or
paints. Refer to the tables then answer below, what is each mineral used for? (15)
Mineral
K-feldspar
Halite
Muscovite
Galena
Hematite
4
Chemical Formula Industrial Use __or__ Ore of Geological Occurrence
L. Tenacity describes the response of a solid substance to applied force such as
pressing on it firmly, bending it or striking it. It is really a composite property that
depends on the strength of bonds, crystal structure, habit of the mineral and even
the direction or strain rate of the applied force. Obtain the following substances and
test their tenacity to familiarize yourself with the various types of behaviour.
Malleable means that something deforms and can readily be folded or bent. Brittle means
it cleaves, crumbles, shatters or fractures. Sectile means it can be readily cut with a knife
like cheese or butter or separated into sheets or fibers. Elastic means when you remove
the applied force, ie stop pushing or pulling, it returns to its original shape. Most minerals
are elastic solids and readily vibrate to pass seismic waves like bells or drum heads.
Plastic means the material has a finite yield strength, so it holds up to a point, then bends
and stays bent out of shape! Describe the tenacity of each of the following items then use
these terms to describe the response of minerals to similar applied forces. (7)
1. Aluminum Can _____________________________________________________
2. Ice cube ___________________________________________________________
3. Rubber band or lab “cork” _____________________________________________
4. Wax Candle _________________________________________________________
5. Copper foil or sheet ___________________________________________________
6. Native Sulfur ________________________________________________________
7. Halite ______________________________________________________________
Activity 3.2: Analysis and Classification of Crystal Forms
Background: natural crystals can make a variety of stunningly beautiful forms. Their
external form depends on their internal atomic or molecular structure and environmental
factors during their crystallization and growth like fluids, availability of the right
compounds, interference with neighboring crystals, changing impurities, temperature or
chemical gradients, supersaturation etc. For example note the variation in ice crystal
morphology as a function of the temperature of freezing and the relative humidity
(saturation of water vapour) in the graph below and then examine these photos of actual
snowflake crystals a on left for question 1 and b on right for question 2.
5
A. Analyze the photos of snowflakes and other crystals on p 81. Refer to the definitions
of Habits in table 3.4 and geometric crystal forms in Fig 3.5 as well as other photos in
the manual or above a and b to answer the following questions: (5)
1. What is the habit of the upper snowflake (a left one above)? Note that more than
one term might apply. ____________________________________________
2. Find a mirror plane across this snowflake (there are actually 2 different ones),
trace it on the photo a above and colour the 2 halves of the snowflake in different
colours.
3. Real natural crystals have imperfections in their outer faces do to changing
environmental conditions while they grew. The graph above explains the
influence of some of these for ice crystal forms. Impurities, thermal or chemical
gradients, and interference by neighboring crystals also wreak havoc. To which
crystal system do these snowflakes belong?
How do you know?
6
B. Other common materials have inherent crystal symmetry due to the structural
arrangement of their molecules (ice, sugar), ions (halite, epsomite) or atoms (Sulfur, gold,
copper, carbon). Examine the photos and name the crystal system for each one. (3)
1. Sucrose (left) belongs to the ________________ crystal system.
2. Epsomite (centre) belongs to the _____________ crystal system.
3. Halite (right) belongs to the _________________ crystal system.
Activity 3.3: Determining mineral density &specific gravity
D. Obtain specimens from our collection and measure their densities and specific
gravities using graduated cylinders and small well crystallized specimens containing only
1 type of mineral that will fit inside! Heft them to get a qualitative idea of their sg’s (light
<3, 3<intermediate<4, heavy>4). Fill out the table below give 3 significant figures. (12)
Mineral Name Mass
(g) Volume (mL) Density g/mL Specific Gravity
Sulfur
Fluorite
Galena
Activity 3.4: Economically important minerals & working with our
collection and the web
A. Find specimens of calcite and siderite. Describe or measure the following
properties then explain how these minerals can be distinguished. (12)
Mineral
Formula Habit/Form
Streak
S.G.
Acid Reaction
Calcite
Siderite
Explain the best tests:
________________________________________________________________________
________________________________________________________________________
7
B. Find specimens from our collection & measure these properties. (20)
Almandine garnet Formula
Habit/Form
Hardness
Specific Gravity
Barite
Corundum
Epidote
Olivine
Tourmaline
C. Obtain specimens of Hornblende and Augite which display good cleavages.
Make the following tests then draw each specimen and explain how they can be
distinguished? Hold the crystals up to the template in the back. (20)
Mineral
Formula
Habit/Form Cleavage Angles
S.G Hardness
Augite
Hornblende
Explain the best tests:
________________________________________________________________________
________________________________________________________________________
Labelled Drawings:
D. Obtain specimens of 3 phyllosilicates (micas): Muscovite, Biotite and Chlorite
(Clinochlore). Make the following tests then draw each specimen and explain how
they can be distinguished? (17)
Mineral
Formula
Habit
Streak Hardness
S.G.
Biotite
Chlorite
Muscovite
Explain the best tests:
________________________________________________________________________
________________________________________________________________________
8
E. Feldspars make up over half of the crust and distinguishing them is important to
classifying rock types. Read P.68 & figure 3.15 then obtain specimens of 3 different
feldspars, test their properties, draw a plagioclase (albite, andesine, labradorite) and
an alkali feldspar (orthoclase, microcline) and label how they are distinctive due to
either multiple polysynthetic albite twinning or perthite exsolution lamellae. (10)
F. Find and learn to distinguish the following important ore minerals from our
collection, as you do so read about them in the tables or on line and fill out the table
below. (24)
Mineral
Chemical
Group
Formula
indicate
Use/application
ore element
or occurrence
Cassiterite
Pegmatites &
Placers
Chromite
Ilmenite
High strength
alloys
Chalcopyrite
Sphalerite
([Zn],Fe)S
Quartz
Zircon
9
Geological
setting
Nonferromagnesian
silicates
G. Mineral Resource Web exercise (1 page): Choose a mineral resource such as:
Diamond, Gold, Halite, Sylvite, Chromite, Chrysotile asbestos etc., What rock types and
geological setting does this mineral form in (tectonic location, physical and chemical
conditions of formation, associated minerals)? What if any are the environmental issues
for this mineral or its production? What economic or industrial uses does it have? Are
their any human health issues associated with its mining or use? Use chapter 20 in the
text and a website called Mindat.org because much of the other information on the web is
misleading, incomplete biased or just plain wrong. (10 points)
10