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 a streak test better than color?
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 above, do not have streak. To check streak, scrape the mineral across an unglazed porcelain plate (Figure below).
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.
Why is streak different from color?
Streak is closely related to color, but is a different property
because the color of the mineral may be different than the color of the streak
. Streak is actually the color of the powder of a mineral. … Many opaque minerals similarly have a rather unhelpful black streak.
Which is more reliable in identifying a mineral?
Streak
is more reliable than color to identify minerals. The color of a mineral may vary. Streak does not vary. Also, different minerals may be the same color, but they may have a different color streak.
Which is more reliable color or streak?
The color of a mineral in powdered form is called the mineral’s streak. To find a mineral’s streak, the mineral is rubbed against a piece of unglazed porcelain called a streak plate. … For this reason, streak is more
reliable than color
as an indicator of a mineral’s identity.
What mineral is black?
| Mineral Name Color Streak Color | Aguilarite # black black, grayish | Pseudobrookite # black brown | Bracewellite black brown, dark | Loparite-(Ce) # black brown, reddish |
|---|
Why is streak more reliable for identification?
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 above, do not have streak. To check streak, scrape the mineral across an unglazed porcelain plate (Figure below).
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.
Why would a mineral not leave a streak?
Streak plates usually have a Mohs hardness of between 6.5 and 7. … Instead of leaving a powder behind when dragged across a streak plate, they will scratch the streak plate or fracture into small pieces.
Minerals that are harder than the streak plate
are said to have “no streak” or a “colorless streak.”
Why is it difficult to identify a mineral by its color?
Color. … Generally, color alone is not the best tool in identification
because color can be highly variable
. Some minerals can occur in a variety of different colors due to impurities in the chemical makeup of the mineral.
What is the least useful mineral property?
–
Streak
is the least useful property for identification, as the same mineral type can be found with several different colors of streak due to impurities in the mineral.
What is the softest mineral?
Talc
is the softest and diamond is the hardest. Each mineral can scratch only those below it on the scale.
What is the hardest known mineral on Earth?
Diamond
is the hardest known mineral, Mohs’ 10.
Why do we need to check for more than one property in mineral identification?
A mineral’s appearance helps identify it
.
However, many minerals occur in more than one color, so you would need to examine other properties as well. You might also notice how the mineral reflects light, which determines how shiny or dull it is. Most minerals reflect light in characteristic ways.
What are the two main types of luster?
There are two main types of luster:
metallic and nonmetallic
. There are several subtypes of nonmetallic luster, namely vitreous, resinous, pearly, greasy, silky, adamantine, dull, and waxy.
