Identification Of Minerals - Physical Science Laboratory

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Physical Science 111
Physical Science Laboratory: Identification of Minerals
Objective: After successfully completing this laboratory you will be able to identify several common minerals according to their
properties.
Materials: 26-piece mineral set with a porcelain scratch plate, a small magnet, a magnifying glass and a dropper bottle of 3M HCl
(hydrochloric acid).
Instructions: Obtain a box of minerals from the instructor and spread the samples out on the laboratory bench. These mineral samples
have numbers painted on them. Arrange the minerals in numerical order. These numbers are for reference only and are NOT related to
the Mohs hardness scale or any other mineral property. You should have 26 different mineral samples.
Goal: Your goal is to identify these minerals based on deduction and careful observation of their properties. Record your conclusions
on the MINERAL IDENTIFICATION CHART (next page).
Detailed Instructions – Step by Step:
1.
Find the micas. There are two mica minerals; biotite and muscovite; in the mineral set. The micas can be easily recognized
because they easily cleave into thin sheets. They look like “plastic”. One sample is dark due to the presence of iron (biotite)
and the other is translucent (clear). Record these names on the chart next to the correct numbers. (2 samples)
2.
Next find sulfur. Sulfur is easily recognized because it is pale yellow. Our samples are not crystalline – they are in the form
of a clump – and they are opaque not translucent. If you rub the sulfur against the unglazed porcelain you might smell
hydrogen sulfide (rotten eggs). Enter sulfur into your chart in the correct numerical slot. (1 sample)
3.
Now look for galena. Galena has the chemical formula: lead sulfide (PbS). It is shinny and metallic and dense (seems
heavy). It has cubic cleavage. You will see flat surfaces at right angles to each other (little cubes). It has a grey streak. Rub it
on porcelain to see the streak. Add this mineral to the chart in the correct slot. (1 sample)
4.
Now look at the minerals numbered 6,7,8,9 and 10. Three of these are different kinds of hematite: massive (opaque with poor
*
crystal form), oolitic
and specular ( it sparkles). The other two samples are limonite and magnetite. Magnetite is a natural
magnet. Your sample may attract a paper clip but our samples have weak magnetic fields. It is black and will stick strongly to
a magnet. Use the streak test to find limonite. Limonite has a yellow-brown streak while hematite has a reddish brown streak.
Magnetite and hematite are oxides of iron (rust), limonite is also an oxide but it contains some hydrogen so it is also part
hydroxide. Add these iron ores to your chart. (5 samples)
5.
Next separate out the following numbers: 1,2,3,4,5,11,16, 18 and 19. All of these samples are on the Mohs hardness scale.
You will NOT find diamond, corundum (ruby), topaz or apatite in our mineral sets. This leaves talc, gypsum (two types:
selenite and massive), calcite, fluorite, feldspar and quartz. Use the scratch test to identify the relative hardness of these
minerals. Here are a few clues to help with identification. Calcite fizzes when a drop of hydrochloric acid is placed on it
because calcite is calcium carbonate and the acid releases carbon dioxide gas bubbles from this mineral. Talc feels greasy and
is very soft and easily crushed into powder (talcum powder). There are two types of quartz – one is translucent and crystalline
and the other is milky and pink (rose quartz). There are two feldspar samples - one is pinkish and one is gray. The pink one is
orthoclase and the gray one is plagioclase. (9 samples)
6.
Next look for the pyrites. There are two of them. One is iron sulfide (pyrite) and one is copper iron sulfide (chalcopyrite).
These minerals are referred to as “fool’s gold” because they look a little bit like gold. Iron sulfide has a more golden color
while copper iron sulfide has a reddish or greenish hue. (2 samples)
7.
Now carefully examine the remaining minerals. What remains is olivine (greenish), halite(salt, cubic cleavage), serpentine
(snake like patterns), hornblende (black or greenish), sphalerite and garnet. Use available pictures to help you identify these
minerals. (6 samples)
* Oolites are tiny round spheres of chemically precipitated hematite.

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