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Mineral Identification Summary

Four requirements for a material to be classified as a mineral are the following: it must be an element or a chemical compound; it must be solid; it must have a definite crystalline structure; and a biological process should form it (Jessey & Tarman, 2006).

Based from the information gathered, we can determine and differentiate the identity of a mineral by recognizing its color and streak, computing for its specific gravity, observing its luster, knowing whether it cleaves or fractures, testing its hardness, and verifying if it reacts to hydrochloric acid.  In identifying the color of a mineral, we just have to determine the dominant and obvious color of the material. Although it is a noticeable characteristic of a mineral, it should never be its defining attribute since impurities can cause so much change in its color and it might fool us.  In identifying the streak of a mineral, we must determine the color of the mineral in its powdered form.  One can literally pulverize it or just drag it across a very rough plane and see its color.  It may or may not take the color of its crystallized for. So, don’t just conclude that the color of the streak is the same as the color of the dominant color.

The luster of a mineral can be described as dull, pearly or shiny depending on its overall gleam and how much it can absorb and reflect light.  Specific gravity is one the extrinsic property of a mineral since a certain mineral has its own distinct specific gravity (that’s why it is called ‘specific’).  It can tell right away the identity of the mineral if you already know the specific gravity of different minerals.  If a mineral has even and almost smooth surface after it breaks into pieces, that means it cleaves. Otherwise, it fractures.  The resistance of a mineral against scratching can test its hardness.  The acid test verifies if a mineral contains calcium carbonate.  Hydrochloric acid is often used in this kind of test.

            Basically, a rock is a blend of different minerals but it can also be formed by a single and pure element or chemical compound.  Hence, the difference between a rock and a mineral is that the former is the combination of the latter.

Reference

Jessey, D. & Tarman, D. (2006). Mineral Identification: the Beauty of Nature. Retrieved May 30, 2008, from http://geology.csupomona.edu/alert/mineral/minerals.htm

Part 1: Recording Observations

In the chart below, record your observations of each test for the seven minerals. After you have completed all tests, name the minerals in Part 2 of this worksheet. An example of how to fill out the chart is illustrated below.

Recorded Observations for Minerals 1-7
Tests
Example
Mineral 1
Mineral 2
Mineral 3
Mineral 4
Mineral 5
Mineral 6
Mineral 7
Color
White
white
green
white
pink
gold
white
black
Streak
White
black
white
white
white
white
white
brown
Luster
Shiny
pearly
pearly
shiny
dull
shiny
shiny
dull
Specific Gravity
3.18
5.1
2.8
2.7
2.6
2.65
2.4
2.2
Cleavage & Fracture
Cleavage
Fracture
Fracture
Cleavage
Fracture
Fracture
Cleavage
Cleavage
Hardness
4
3.1-5.9
1-2.9
1-2.9
3.1-5.9
6.1-10
1-2.9
1-2.9
Acid
No Reaction
No Reaction
No Reaction
Active Bubbling and Fizz
No Reaction
No Reaction
No Reaction
No Reaction

Part 2: Naming the Minerals

Name the minerals below. Then, insert a percentage of how certain you are in your identification. Finally, explain your percentage of certainty: What was confusing about this mineral? What other minerals do you think it could be?

Remember, the minerals in the virtual lab include seven of the following: borax, calcite, corundum, graphite, gypsum, orthoclase feldspar, pyrite, quartz, talc, and topaz.

Identification of Mineral
Percent Certain
Explanation of Certainty
Example: Fluorite
80% certain
I am almost certain this mineral is fluorite, but I am not complete sure. Fluorite and gypsum are both white, shiny, have white streaks, cleave, and show no reaction to acid. However, the specific gravity of this mineral is 3.18, which is higher than gypsum, so I am pretty sure it is fluorite.
Mineral 1:  Pyrite
86%
The only factor that disagrees with a Pyrite’s description is the color so I’m certain that it is Pyrite.
Mineral 2:  Talc
100%
It has all the characteristic of Talc.
Mineral 3:  Calcite
100%
It has all the characteristic of Calcite.
Mineral 4:  Orthoclase Feldspar
100%
It has all the characteristic of Orthoclase Feldspar.
Mineral 5:  Quartz
86%
The only factor that disagrees with a Quartz description is the color so I’m certain that it is Quartz.
Mineral 6:  Gypsum
100%
It has all the characteristic of Gypsum.
Mineral 7:  Graphite
57%
Although the color, luster and the cleavage is very different from a graphite, I chose it because it scored 4 out of 7 attributes but more importantly because they have the same specific gravity which is 2.2. Specific gravity is unique to each and every mineral.

 

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