The test described is called a streak test, and indicates the true color of a mineral as observed in a powdered form.
streak
They both help to identify a mineral
Yes
The cleavage of a mineral is the characteristic manner in which it splits along crystallographic structural lines or planes. Cleavage alone is not sufficient to be able to identify a given mineral, but it is a solid clue which, when combined with a few other characteristics, will allow an investigator to identify a mineral. The notation of cleavage will eliminate some minerals and lead the way to being able to categorize a given mineral as something else. A link can be found below.
Microline is a mineral that has been used as a semi-precious stone. It has been called Perthite and Amazonite. Microline is used in making porcelain.
By rubbing mineral against a piece of porcelain tile, the objective of the test is to observe the hardness of the mineral.
That procedure tests the streak of the mineral. Oddly, the streak color of some minerals are different from the mineral's color.
The test is called a streak test and it leaves a powdered form of the mineral on the porcelain. The powdered mineral reveals the true color, of the mineral specimen, which may or may not match the color of the specimen.
You identify minerals through a streak test. This involves taking the tile and the mineral to be identified and rubbing them together. This produces a colored streak on the tile, which can be used to identify the mineral. Consult a field guide for specific colors.
Which mineral leaves a green-black powder when rubbed against an unglazed porcelain plate?
StreakColor of the mineral when it is powdered.Grind a small amount of a mineral into a powder on a porcelain streak plate and determine the color of the powder.
hardness
Porcelain, as the name suggests.
Streak tests are used to identify minerals. Rubbing a mineral specimen against unglazed white porcelain, or finely powdering it and examining the powder against a white background, is a useful diagnostic test in some cases. Eg. hematite, a black mineral that looks much like many other black minerals, has a distinctive red streak.
Mineral samples can be scraped across the bottom (i.e., the unglazed side) of a tile to create a colour streak which is characteristic of the mineral. Note that it takes more than a colour streak to identify a mineral. Many minerals have the same colour streak. Other characteristics such as the hardness and density will also need to be determined in order to positively identify a mineral.
By rubbing a mineral against a piece of unglazed porcelain tile From Prentice Hall textbook: Inside Earth
hematite