You have a rock of unknown origin and composition.
a) what three test would you perform to determine what type of minerals are part of the rock?
b) what characteristics is being examined in each test?

You use methods in everyday life, so when finding the type of minerals that are part of a rock you use many methods, that is, you apply tests that says to you the origin and composition of the rock. So let's study three of that methods.

A.1 Lustre

First of all, I would use this test because this is the way light reflects from the mineral's surface. You can have minerals that are metallic (shiny) or non-metallic (not shiny). The origin of this word comes up of the Latin lux that means light and generally implies radiance, gloss, or brilliance.

A.2 Streak

Other important test I would use is the streak (also called powder color). The streak of a mineral is the color of the powder produced when it is dragged across an unweathered surface. 

A.3 Hardness 

I would use the hardness to determine what type of minerals are in the rock. In this test you measure the ease with which a smooth surface of a mineral can be scratched or the resistance to abrasion.

B.1 Characteristic of lustre test

Lustre (also called luster) depends on a mineral’s refractive power, diaphaneity (degree of transparency), and structure. You may obtain different kinds of lustre for variations in these properties. On the other hand, variations in the quantity of reflected light will produce different intensities of the same lustre. Minerals with a metallic lustre like gold, tin, copper are usually opaque and have refractive indices near 2.5. Adamantine, nearly metallic lustre of diamond and other transparent minerals have refractive indices between 1.9 and 2.5. The most common lustre in minerals is vitreous that has refractive indices between 1.3 and 1.8, just as in quartz. There are other type of lustre like resinous (the lustre of yellow resins), greasy (the lustre of oiled surfaces), silky (minerals with a fibrous structure have this lustre), dull (without lustre).

B.2 Characteristic of the streak test

If you rub the mineral on a white, hard surface, just as a such as a tile of unglazed porcelain. This yields a line of fin powder. The main characteristic is that the color of the streak is usually constant for a kind species of mineral, even though the mineral may vary in color as it happens in the field. In this way, this is an important diagnostic tool in mineral identification because the trail of finely ground powder has a more consistent color unlike the apparent color of a mineral. Therefore, streak is one of the more useful diagnostic properties given that it is a quick way to identify different species of minerals that are otherwise similar in appearance.

B.3 Characteristic of the hardness test

In this test there is a method called Mohs' scale of hardness invented by the Austrian mineralogist Friedrich Mohs. It's a scale based on one mineral ability to scratch another. In principle, Mohs designated 10 minerals from this scale from hardest (10) to soft (1). The test consists in the use of moderate pressure. So you need to drag a sharp edge over the smooth surface of a mineral. Then, If the surface of the mineral is scratched then it is softer than the material used to scratch it, if not then it is harder.

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