Geology 1010 Labs
Geology 1010 – Instructor
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Dr. David McMullin
Office: HSH 305
Phone: 585-1276
Email: david.mcmullin@acadiau.ca
Office hours: M, W, F, 11:30 – 12:30
Lab assistants
• Tuesday: Jackson Malone, Jon Shute
• Wednesday: Patrick Henger, Rachel Lewis
• Thursday: Margot Aldis
Schedule
• 10 labs and one final exam (11 in total)
• Three sections
• You must have permission to switch to
another lab section (even for one week)
• All lab info on ACORN and lab web site.
• All labs are to be handed in at the end of
the lab session
• Returned to you at the beginning of the
next one
Things on the lab web page
• Lab answer keys
– posted after the last lab in the series
• Hardness “exercise”
• Geological time scale
• PowerPoint files of these pre-lab
presentations (including this one)
• Mineral database (Access)
• “Digital learning objects”
http://socrates.acadiau.ca/courses/geol/1013/labs/
FOIPOP Act
• Graded labs/assignment are considered
private property and subject to FOIPOP
act
• Graded labs with therefore only be
handed back in lab
Laptops
• All lab tests are open book (open laptop)
• Bring your textbook to all labs (except field
trips)
• Bring your laptop to all labs (not necessary
on field trips)
• Please do not use laptops for non-lab
reasons during the lab introductions
– Once I’m done you can IM, text, listen to
music, whatever, as long as you don’t disturb
your neighbours
Some personal philosophy
• The important thing about any given lab is
not to get it done (the end result),
but the doing of it (the process).
• It’s the process that’s important and one I
hope you will bring to new challenges, new
opportunities, new situations, new
subjects, … for the rest of your life!!!
• We tend to lose sight of this because it is
the end result that can be graded, but the
end result is not what matters most
Questions?
Minerals
• Your textbook defines a mineral as:
– an inorganic,
– naturally occurring,
– crystalline solid (homogeneous solid in
which atoms are arranged in a definite
order) with a
– narrowly defined chemical composition and
characteristic physical properties.
Minerals are inorganic
• Minerals can be formed (secreted) by
organic processes but
• Materials that require organic
processes/activity are not minerals
– Sugar is not a mineral, nor is coal, etc.
– But teeth are dominantly composed of the
mineral apatite (Calcium phosphate)
Minerals are naturally occurring
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Synthetic analogues of minerals are
usually prefaced by the term “synthetic”
– E.g. synthetic ruby, synthetic diamond, etc.
Minerals are crystalline
• Homogeneous
• Solid
• Ordered atomic arrangement
– Quartz is a mineral but glass made from
quartz is not (quenched liquid)
– water is not a mineral but ice is
– Liquid mercury is not a mineral but mercury
oxide is
Minerals have definite
compositions
• Many minerals show variation in
composition but only within specific limits
tightly controlled by their crystalline nature.
– E.g. Mg2SiO4 to Fe2SiO4 (olivine)
Mineral identification
• Physical properties, which are controlled
by the crystalline nature
• Mineral identification has gone on for
thousands of years using very basic tools
• Now there are many highly sophisticated
methods
• But we will be using a few basic tools and
your powers of observation
Tools
dilute HCl
hand lens
streak
plate
Cu pennies
nail
magnet
glass plates
Physical properties
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Lustre
Hardness
Streak
Cleavage/fracture
Colour
Specific gravity
Others
Lustre
• The way light reflects off the mineral
surface. For our purposes we will define
only two types of lustre
– Metallic (has a metallic sheen or
appearance)
– Non-metallic
• The identification chart (handout) splits
the minerals into non-metallic light, nonmetallic dark and metallic
Lustre
• There are many types of non-metallic
lustre. See the display at the back of the
lab. Some examples:
– Vitreous (glass like)
– Porcelainous (like porcelain)
– Pearly
– Silky
– Resinous
– Waxy
Hardness
• The crystalline structure of mineral leads
them to have very consistent hardness
• Hardness scale puts minerals on a scale
of 1 to 10 in terms of their ability to scratch
or be scratched by others
• Talc has a hardness of 1, diamond is 10
• Hardness scale on Socrates is:
http://socrates.acadiau.ca/courses/geol/1013/labs/mohs/mohs.html
Hardness
• We use a series of simple tools to get an
estimate of hardness
• Fingernail (approx. 2.5)
• Copper penny (approx. 3)
• Glass plate and steel tool (both approx. 6)
– For our purposes the most important standard
is whether it is harder than glass (scratches it)
or softer than glass (can be scratched by steel
tool)
Streak
• Streak is the colour of the ground-up mineral
• Found by rubbing the mineral on the streak plate
• Can only be done with minerals with hardness <
6
– Why?
• Many metallic minerals have a diagnostic streak
• Most non-metallic minerals have a white streak
Cleavage/fracture
• The way in which a mineral breaks
• Because of the highly ordered atomic
structure, many minerals have systematic
planes of weaknesses = cleavage
• A mineral with one cleavage breaks along
a single set of smooth and parallel fracture
surfaces which results in a platy
appearance
One cleavage (platy)
Cleavage/fracture
• A mineral with two cleavages show two
sets of smooth parallel fracture planes at
some angle to one-another which
commonly results in a rod-like appearance
Two cleavages (at right angles)
Cleavage/fracture
• A mineral with three cleavages shows
three sets of parallel planes at angles to
one another. Such a mineral will break into
– cubes (if the planes are at right angles to one
another) or
– rhombs (if the angles between the planes are
not equal to 90°)
Three cleavages
Cubic cleavage
(e.g., salt)
Rhombohedral cleavage
(e.g., calcite)
Cleavage/fracture
• Minerals with 4 or more cleavages are
relatively rare and it is difficult to see all
the cleavages
• Four cleavages produce octahedra (8
sided fragments)
• Six cleavages produce dodecahedra (12
sided fragments)
Four cleavages
Cleavage/fracture
• Some minerals do not have cleavage
planes and show a random orientation of
fracture surfaces
• Some minerals without cleavage break
with curved surfaces that show ribbing like
a shell surface. This is conchoidal fracture
Conchoidal fracture
≈60°
Colour
• Colour is often not a diagnostic
property.
• Colour variations are most commonly
the result of small amounts of impurity
• Light coloured non-metallic minerals are
more prone to colour variations. Quartz
is found in the following colours:
Red (carnelian, jasper), pink (rose
quartz), purple (amethyst), yellow
(citrine), black (smoky quartz),
green+red (bloodstone), etc.
Colour
• Do not confuse the terms “colourless” and
“transparent”, they are not the same.
– window glass is transparent and colourless
– sunglasses are transparent but coloured
• Transparent: you can see through
• Translucent: allows (some) light through but one
cannot see through (e.g., frosted glass)
• Transparent objects may coloured or colourless
• Translucent and opaque minerals are coloured
Specific Gravity
• Ratio of the density of the mineral to the
density of water
• Minerals have specific gravities that vary from
about 2.5 to 19 (gold).
• Non-metallic light minerals are generally light
(SG = 2–3). There are exceptions and such
variation is often diagnostic (e.g., barite:
SG=4.5)
• Non-metallic dark minerals generally have
moderate (or average) specific gravity (3–4)
• Metallic minerals are generally heavy or very
heavy (SG = 5+)
Other properties
• There are many other properties that
minerals can have and they are often
diagnostic. A few important ones to watch for:
– Magnetism (e.g., magnetite)
– Reacts with dilute acid to produce CO2 (e.g. all
carbonate minerals to varying degrees)
– Tarnish (various metallic minerals)
– Fibrous appearance (asbestos)
– Iridescence (e.g., plagioclase)
– Smell (clay minerals)
– Taste (salt)
Doing the lab
• Fill in the blank spaces in the lab handouts
• Many of the spaces are already filled in. Don’t
skip these, they are intended to help you
learn.
• Make sure you understand why each given
property is as indicated. For example, #1 is:
– Metallic
– Has a hardness greater than a penny, less than
glass
– Has a black streak
– Etc.
Doing the lab
• Use the identification charts (handout)
to name the mineral and give its
composition.
• Look at the examples at the back of the
lab.
• Ask questions. We will try not to give
you flat out answers. Rather we will
encourage you to observe and deduce
the answers for yourself.
• Lab sheet is due at the end of the lab
session.
One final point…
• Enter your observations NOT what
you’ve read in the ID chart
• E.g., for hardness put “>glass” not “7”
(you can determine that something is
harder than glass you cannot determine
an absolute number)
• E.g., for specific gravity, put “H” (heavy,
high) not “5.7”
• Etc.
Questions?