SCI121: U2: L2:

color

It is a property of minerals that can be identified easily. The result of how minerals absorb light. Although it is the easiest property used to identify minerals, it is also the least useful or reliable property in identifying minerals. It is because some minerals contain impurities and are affected by weathering which can affect the ______ of the minerals.

streak

It is the color of a mineral in its powdered form, which can be different from its surface color. To find a mineral’s _____, you rub it on an unglazed porcelain plate. This test helps reveal the mineral’s true color, even if impurities affect its appearance.

luster

It is a property of minerals that describes the quality and intensity of light being reflected by the mineral. It determines how the mineral reflects light. It can be described either as Metallic or Non-Metallic Luster.

metallic

Minerals that exhibit this type of luster reflect light like a resplendent shine similar to a polished metal. Exhibiting this luster does not mean that the mineral is composed of metallic elements.

non-metallic

Minerals that exhibit this type of luster do not reflect light very well. This can be described as vitreous (glassy), resinous, silky, pearly, dull (earthy), greasy, etc.

Hardness

This measures a mineral’s resistance to scratching, using the Mohs Scale from 1 (softest) to 10 (hardest), developed by Friedrich Mohs in 1822. Each number corresponds to a specific mineral’s hardness. Household items can also test hardness by scratching the mineral to create a permanent mark.

Cleavage

This is a mineral’s ability to break along specific planes to form smooth, flat surfaces. This happens where the crystal structure is weakest. This is described by the number and angles of these break directions, such as two directions at 90 degrees.

Fracture

This is how minerals break when they don't cleave along smooth planes. It describes the irregular, non-planar surfaces that form when minerals chip or break. All minerals can have this, and these breaks are described as conchoidal, uneven, or hackly.

Specific Gravity

This is the ratio of a mineral’s weight to the weight of an equal volume of water. It measures density: water has a specific gravity of 1, so a mineral with a specific gravity of 3.5 is 3.5 times heavier than water. Minerals with specific gravity under 2 are light, 2–4.5 are average, and above 4.5 are heavy.

Magnetism

It is the tendency of a mineral to be attracted to magnets. A mineral that exhibits attraction to a standard magnet is considered magnetic. The mineral Magnetite (Fe3O4 ) is a mineral that shows attraction to magnets, hence the name Magnetite.

Odor

Some minerals have a distinct smell, like sulfur, which smells like rotten eggs. However, this is rarely used for identification because some mineral smells can be harmful.

Taste

Certain minerals, such as halite (table salt), have a recognizable taste, but tasting minerals is not recommended since many are unsafe to eat. This is rarely used for identification.