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Welcome to Practice 12. We're going to look at the physical properties of minerals and

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how they're found both in the natural world and their composition. So, the minerals are

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here. Minerals are naturally occurring inorganic substances, which form rocks of the Earth's

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crust. The physical properties of minerals reflect their chemistry and internal structure

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and provide keys to their identification. Some chemical properties may be determined,

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such as testing for a reaction with hydrochloric acid or determining the density and specific

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heat of the mineral. With knowledge of both these characteristics, identification of minerals

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becomes much easier. The most common rock-forming minerals can be identified by some key properties.

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In today's lab, you will test minerals for some of these key characteristics. So, we

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will look at color. We'll make a streak test. We'll look at luster, cleavage, hardness,

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and we will make, on certain minerals, a chemical test, which we will place a drop of hydrochloric

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acid and see whether or not the chemical reacts with bubbles to the mineral at that time.

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In this lab, we're going to use minerals. We're going to use a porcelain tile that's

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white for the streak test. We're going to use glass and a copper wire and our own fingernail

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to test hardness of the minerals and whether or not they can be scratched based on a scale

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with our fingernail, with copper wire, or with glass, which will tell us about how hard they

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are. The next mineral we're going to look at is a very common mineral. This is graphite,

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and we put it in pencils. We use it all the time, and it's a mineral we find often in nature. It is

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quite common and quite useful. So, we're going to look at five important characteristics. First of

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all, we look at the luster. Luster is whether or not it is dull, metallic, shiny, and this is a

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dull mineral. It is not shiny. It is not crystal. The color is gray, and when we make a streak test

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with graphite, placing it on the porcelain tile, we can see a streak of black. So, we know that

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it is the streak test would be black, and for hardness, the first test we make is of a human

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fingernail, and we can see that a human fingernail can scratch graphite. So, we know that it is very

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soft, and on the number scale of very soft to very hard, it is a one or two rating of softness.

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Finally, we test for density. So, we feel for weight and density, whether or not it's heavy

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or light, and this mineral is light. So, that is the physical testing of the mineral graphite. This mineral is

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called galena, and again, we're going to do the physical testing. So, first of all, we look very

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simply at the mineral. Its luster is not dull like the graphite. Instead, it is metallic. Its color

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is black, white, brown, but predominantly black, and when we use it for the streak test on our

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porcelain tile, we can see that it leaves a black streak. In terms of hardness, if at first the

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fingernail has no effect, the copper wire is equally incapable of scratching, and then with the glass,

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we can see that the glass can make scratches on the galena. So, we would categorize this mineral

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as hard of a rating five to six, and when picked up, the density is that of a heavy mineral. So,

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this is heavy, black, it's hard, five to six, and it leaves a black streak. Cinnabar is a mineral

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that is characteristic with its dark red coloring. Its luster is metallic. The color, as we said,

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is a dark red, and when taken for the streak test, we can see that it leaves a red, brown, brownish

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red streak. Its hardness cannot be scratched with a fingernail. Copper wire is capable of

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scratching it, so it is considered a soft mineral with a rating of three to four, and it is a middle

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type of heavy for its density. Pyrite is colloquially called fool's gold because of its

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shiny gold-like luster, so we know that it has a highly metallic luster. It is dark brown or black,

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and its streak test is a clear black streak. For its hardness, we can test it. Fingernail makes

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no effect. Copper wire, it's equally impossible to scratch. Even glass does not scratch the pyrite,

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so we can categorize this as a very hard mineral, and its density is that of a heavy mineral.

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Halite is another common mineral. It is rock salt. Its luster is non-metallic. It's gray,

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although very crystallized, and its streak test is white. It leaves a white streak on the porcelain

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tile. In terms of hardness, a fingernail has no effect, but the copper wire can streak it,

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can scratch it, so we know that it can be categorized, again, as soft, so a three to

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four rating, and in terms of density, it's remarkably light. Orthoclast is a non-metallic,

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light brown mineral, and its streak test leaves a white streak, very difficult to see on the tile,

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and this mineral cannot be scratched with a fingernail, cannot be scratched with the copper

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wire, cannot be scratched with glass. It is very hard, so it is one of the hardest minerals we have

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tested yet, with its physical properties, and when held, it's surprisingly light, so its density is

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light. Quartz is a very pretty mineral, and it is non-metallic, but very glassy is its luster,

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so it has a glassy luster, and this quartz is pink. It comes in many colors, but we're looking

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at pink quartz right now for color, and no matter what color the quartz, its streak test is white.

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It cannot be scratched by a copper wire, it cannot be scratched by glass, and this mineral is so hard

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that it can actually, it is capable of scratching glass, so you can see the scratch that it made.

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It is one of the hardest minerals, and it is capable of scratching glass. Another pretty

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mineral is mica. It is very shiny, so it has a highly metallic luster, and the color is a light

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gray or brown. When it makes it for its streak test,

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it leaves a white streak. Shouldn't it be leaving a brown streak right now? It leaves a white streak,

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and in terms of being soft, a fingernail cannot scratch it, but the copper wire can,

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so it is considered a soft mineral, and it is also very light. One of the most remarkable

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physical characteristics of this mineral is that it cleaves in layers. It has layer cleavage,

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so it is very obvious that it will break and even fleck off into layers, which is one of the most

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obvious physical characteristics of this type of mineral. These two types of mica are different

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colors. This is moscovite, and this is viatite, and even though they are white and black,

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they leave the same color scratch, which is white. So although this mica is black,

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it will leave a white scratch, which characterizes it physically as mica. Argonite is a non-metallic

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mineral, so the luster, again, is dull or non-metallic. It is a dark brown color,

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and its streak test produces a white streak. It is scratched by the copper wire, so it is

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considered soft, and it's a light mineral. We're going to test this mineral because of its

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characteristic properties regarding hydrochloric acid. So I have hydrochloric acid in a small

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droplet bottle, and we're going to watch the chemical reaction between the argonite and

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the hydrochloric acid. The reaction is very swift. This is argonite dissolving and bubbling,

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frothing and foaming because of its chemical reactions to the acid on its surface. If this

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mineral were to be immersed in hydrochloric acid, it would dissolve. This glassy mineral is calcite.

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It is non-metallic, but like the quartz, it's very glassy. Its color is white, and its streak test is

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also white. It cannot be scratched by copper wire, but it can be scratched by glass, as we can see.

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It could be considered hard, and it has a chemical composition that reacts to sulfuric acid. We're

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going to test that chemically now with our droplet of sulfuric acid on the surface. You can see it

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immediately reacting to the hydrochloric acid. Carbon dioxide bubbles are being formed on the

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surface, and if this mineral were to be immersed in hydrochloric acid, it would dissolve the way

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that the surface is dissolving and reacting to the single droplet that we're using in this lab.

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Gypsum is a non-metallic, but highly glassy mineral, so its luster is glassy, and its color

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is white, or crystalline, and when it's scratched, the streak test produces a white streak. In terms

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of hardness, this is so soft, it can be scratched by a fingernail, by a human fingernail, so it's

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considered very soft, from one to two, and its density is relatively light.