GEO109_SCI210_Lab 1_Observing Minerals SP22
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GEO 109L – Earth, Environment, & Society Lab
SCI 210L – The Dynamic Earth Lab
Lab Exercise 1: Observing Earth’s Minerals
Lab Exercise
On your table is a box of fifteen mineral samples. These are the samples that you will observe and identify in lab next
week. For this week, you will observe the major physical properties and practice using the tools to test these
properties. As you work with the samples, think about how a particular property helps us understand minerals and
distinguish different types of minerals from each other.
Properties of Color and Light - Color and Streak
Color
of a specific mineral sample is determined by the way in which light is absorbed by that sample. The color of a
specific mineral type can vary greatly depending on the chemical composition and the purity of the mineral
structure. While the great variety of colors that are possible for just one type of mineral makes it sometimes difficult
to use color as a primary tool in identifying a sample, it is still important to observe. It is the most recognizable
property of a sample and one that can be observed with just your naked eye.
The
streak color of a mineral is observed after dragging a sample across an unglazed porcelain plate (a streak plate).
By dragging a sample across a streak plate you are slightly pulverizing the sample into a fine powder and THEN
observing the color of the powder. This does not necessarily mean that the streak color will always be the same as
the color of the hand sample. In fact, the streak is at times a more reliable indicator of a mineral identification.
1)
Pick up a piece of samples 2, 3, 12, and 13. Each person in your group can work with one of these samples. Observe the color and the streak for each sample and record below.
Sample Number
a) Color of sample
b) Color of Streak
2
3
12
13
2)
Why do you think it is necessary to observe both color and streak for a mineral sample? Explain.
Properties of Light and Color – Luster
The luster of a mineral is the way in which light is reflected off the mineral’s surface. Think about how you describe
the 'shininess' of things in your everyday life. How would you describe them? A piece of glass would be glassy. A
quarter is metallic. A piece of wood is dull. A CD is iridescent. These are the same types of terms that you can use to
describe the luster of minerals. It is important to note that all minerals can first be broken down in to two main
categories based on their luster: METALLIC
& NON-METALLIC
.
Lab 1 | 1
NAME: ______________________ Table # _____
Note:
Non-metallic minerals are further described with a specific luster type (See luster handout on your table).
3)
Use the luster information provided on your table to help you describe the luster of the following four minerals. Again, each person at your table can work with one of the samples and then share your observations with your group.
Sample Number
a) Color
b) Luster (Metallic M
or Non-Metallic NM
)
c) Only if Non-metallic (NM), give a specific NM luster type (See Handout).
1
6
11
14
Mineral Structure Properties – Electrical Conductivity
4) Another property that can be used to determine if a mineral is metallic is its ability to conduct electricity. Using a piece of sample #3, complete the electrical connection on the back of the flashlight with a small piece of the mineral. Record what happens below.
Mineral Structure Properties – Hardness
Hardness is described as the mineral surface’s resistance to scratching. It is measured on a relative scale of index minerals, called the Moh’s scale (see handout on table). Hand samples of minerals can be tested using a set of common tools that match given values on the Moh's scale. For the glass plate, scratch the mineral on the plate to see if the mineral is harder than the plate. For the other testing materials, use them to try to scratch the mineral and see which is harder.
5) Use the tools provided and determine the range for the hardness value (number) for each of the four samples listed. Use the table on the back of the Mineral ID handout as a guide. Record your answer for each
sample by placing one check
in the box that best represents the range of hardness for that sample. Sample
Number
< 2.5
2.5 –
3.5
3.5 –
4.5
4.5 –
5.5
> 5.5
5
8
10
12
2
Properties of Mineral Structure – Cleavage and Crystal Form/Shape
The properties of cleavage and crystal shape are used to distinguish the physical shapes by which we observe a
mineral hand sample. If undisturbed, the interior structure of a mineral determines the shape it will naturally grow
into. This is the property of crystal form or shape
. Some minerals, when broken, result in broken pieces that share
in resemblance to a common shape with flat sides or planes. This is the property of cleavage
. Other minerals, when
broken, result in irregular fragments with rough/dull sides, lacking any real commonality. This is the property of
fracture.
The majority of samples in our lab have already been broken for you. You will count the number of flat
sides (
directions
) when cleavage is present. You will determine the natural crystal form if, instead, fracture is
present.
**Remember, crystal form is the shape a crystal grows
into, NOT the shape it breaks into.**
6)
For the samples listed below, first determine whether they present with cleavage or fracture. Then, for the samples showing cleavage, use the information provided at your table to determine the number of cleavage directions. For samples showing fracture, describe the crystal form – ask to see a sample of this if needed.
Sample Number
a)
Cleavage or Fracture? (Choose)
b)
If Cleavage – Number of Directions (see handout)
c) If Fracture – Describe Crystal Form (see Samples from Instructor/Handout)
3
5
6
9
7)
Now that you have familiarized yourself with mineral properties, let’s use Google Earth to take a look at some locations from which we get these materials. You will use Google Earth for various labs throughout the semester, so this is good practice! ●
Download the Google Earth kmz file from Isidore Resources “Mining Sites”, open in Google Earth and open the nested folder. Then click on each push pin to take you to the mining locations listed below.
●
Record the mineral (or name of resource) that is mined at each location. (Right “2 finger” click on push pin to get pop up box with image and link to more information. Or Google search for info.)
●
Record the latitude and longitude, and use the Google Earth ruler tool to estimate the approximate
area (length x width) covered by the mine. (Try to measure only the active mining area – Do not include any waste ponds/piles). Please ask your instructor if you want to double-check what you are looking at on Google Earth.
Mine Name
State
/Country
a)Mineral(s)
b)Latitude
c) Longitude
d)
Est. Area (sq mi)
(Show work: Length
x Width = Area)
Hull-Rust-Mahoning Mine Minnesota, USA
East Milford Mine Nova Scotia,
CA
Cape Flattery Mine
(Google Earth search: Cape
Cape Flattery, Lab 1 | 3
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Flattery Airport, Australia, then zoom out to see beyond the airstrip)
Queensland,
Australia
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