Streak is a more reliable
property than color because streak does not vary
. Minerals that are the same color may have a different colored streak. Many minerals, such as the quartz in the Figure 3, do not have streak.
Why is streak more reliable for mineral identification?
The color of a mineral’s streak is not always the same as the color of the mineral sample, as shown in Figure 4. Unlike the surface of a mineral sample, the streak is not affected by weathering. For this reason, streak is
more reliable than color as an indicator of a mineral’s identity
.
Why is streak more useful?
Streak is particularly
important as a diagnostic for opaque and colored materials
. It is less useful for silicate minerals, most of which have a white streak or are too hard to powder easily. The apparent color of a mineral can vary widely because of trace impurities or a disturbed macroscopic crystal structure.
What is the most reliable method for mineral identification?
The physical properties of minerals are determined by the atomic structure and crystal chemistry of the minerals. The most common physical properties are crystal form, color, hardness, cleavage, and specific gravity. One of the best ways to identify a mineral is
by examining its crystal form (external shape)
.
How are streaks used to identify rocks?
The “streak test” is a method used to determine the color of a mineral in powdered form. … The streak test is done by
scraping a specimen of the mineral across a piece of unglazed porcelain
known as a “streak plate.” This can produce a small amount of powdered mineral on the surface of the plate.
What is the difference between a mineral’s streak and color Why is streak more reliable for rock identification?
Streak is the color of a mineral’s powder. Streak is a more reliable property
than color because streak does not vary
. Minerals that are the same color may have a different colored streak. Many minerals, such as the quartz in the Figure 3, do not have streak.
Why is color often an unreliable property for mineral identification?
Explanation: It is common for one mineral to be naturally found in more than one color. …
Using color alone to identify a mineral could lead to an inaccurate conclusion
. The hardness of the mineral, luster, cleavage, fracture, how it reacts to an acid, and other traits can be used to identify what the mineral is.
What is the characteristics of streak?
Streak is
the color of the powdered mineral
, which is usually more useful for identification than the color of the whole mineral sample. Rubbing the mineral on a streak plate will produce a streak. A streak plate can be made from the unglazed back side of a white porcelain bathroom or kitchen tile.
What mineral is not scratched by a fingernail but is scratched by a copper penny?
| mineral Mohs hardness observations on the minerals | talc 1 very easily scratched by the fingernail; has a greasy feel | gypsum 2 can be scratched by the fingernail | calcite 3 very easily scratched with a knife and just scratched with a copper coin | fluorite 4 very easily scratched with a knife but not as easily as calcite |
|---|
What is the hardest known mineral?
Talc is the softest and
diamond
is the hardest. Each mineral can scratch only those below it on the scale.
What is the least reliable way to identify a mineral?
Color
is the least reliable property for mineral identification. The same mineral can come in a variety of colors and different minerals can be the same color.
Which mineral property is easily observed but can be unreliable when it comes to mineral identification?
The physical properties of minerals are related to their chemical composition and bonding. Some characteristics, such as a mineral’s hardness, are more useful for mineral identification.
Color
is readily observable and certainly obvious, but it is usually less reliable than other physical properties.
Which are examples of tests that can be used for mineral identification?
Geologists use the following tests to distinguish minerals and the rocks they make:
hardness, color, streak, luster, cleavage and chemical reaction
. A scratch test developed by a German mineralogist Fredriech Mohs in 1822 is used to determine mineral hardness.
What is streak on a rock?
Streak,
the colour of a mineral in its powdered form
. It is usually obtained by rubbing the mineral on a hard, white surface, such as a tile of unglazed porcelain, so as to yield a line, or streak, of fine powder.
How do you know if a rock has crystals in it?
If the rock feels lighter than that surrounding rocks, it may be a geode.
Geodes have a hollow space inside
, which is what allows the crystals to form. You can also shake the rock next to your ear to test whether it is hollow. You may hear small pieces of rock or crystal rattling around inside if it is hollow.
Does corundum leave a streak?
Corundum
leaves a white streak
(left), but after wiping (right) it is clear that the plate itself was scratched by the hardness-9 mineral.
