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Streak is a mineralogical term to describe the colour produced by rubbing a piece of mineral against a (porcelain) neutral background.
Since Opal is made from silica spheres, I'd expect a white streak, but meaningless. There may be powdered spheres left behind from the opal structure.
The beauty of opals lies in the fact that they consist of all the colours of the rainbow. The predominant colour is blue, but opals have a variety of colours within, including green, orange and yellow. Those with flashes of red are particularly prized. To see opals, click on the related link below. A list (though not exhaustive) of Opal colours: Cacholong - white like porcelain; Fire Opal - orange to red in colour, semi-transparent; Girasol - transparent blue/white with a ouch of red; Hyalite - colourless; Lechosos - deep green play of colour; Menilite (liver) opal - grey or brown; Mexican waer opal - colourless or yellowish; Milk opal - yellowish, bluish-white, or white; Prase - green coloured; Black opal - can sometimes have been treated to give colour to an otherwise white opal. Opals can be found in Australia, Brazil and fire opal in Mexico.
Corundum has a white streak (colour of crushed mineral powder) but you'll not be able to use the streak test on a streak plate as corundum is much harder (mohs hardness of 9) than the plate (6 1/2).
Corundum has a streak that is usually white. However, it can sometimes leave a light pink or light brown streak depending on impurities present in the specimen.
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Why could the streak of corundum be difficult to determine?
Corundum has a streak that is typically colorless, making it difficult to determine on a streak plate. The hardness of corundum (9 on the Mohs scale) can also affect the accuracy of the streak test, as it can scratch the streak plate instead of leaving a distinct streak.
What are 2 minerals that don't leave a streak on a streak plate?
Two minerals that do not leave a streak on a streak plate are quartz and fluorite. Both minerals have a hardness higher than that of the streak plate, so they will not leave a streak when rubbed against it.
What are the eight ways to identify corundum?
Hardness: Corundum is one of the hardest minerals, scoring 9 on the Mohs scale. Color: Corundum can come in a variety of colors, with red corundum being called ruby, and all other colors referred to as sapphire. Crystal structure: Corundum typically forms in a hexagonal crystal structure. Luster: Corundum has a vitreous to adamantine luster. Transparency: It is commonly transparent to translucent. Cleavage: Corundum exhibits no cleavage, only conchoidal fracture. Specific gravity: Corundum has a specific gravity around 4.00. Refractive index: Its refractive index ranges from approximately 1.760 to 1.772.
Is corundum magnetic?
Small traces of iron are responsible for much of the color found in corundum (saphire) gems. Ruby, however, does not contain iron and will not be affected by a magnet. To be technical however, I should point out that corundum is not magnetic. Corundum will not attract other pieces of iron to itself (as far as I know). To simply answer that corundum is not magnetic would have been misleading.
Why is corundum magnetic?
Corundum, also known as aluminum oxide, is not magnetic. It is a diamagnetic material, meaning it does not have any magnetic properties and is very weakly repelled by magnetic fields.
What color is the streak of corundum?
Corundum has no streak color. Because of being a clear white or light blue, its streak is actually clear.
Why could the streak of corundum be difficult to determine?
Corundum has a streak that is typically colorless, making it difficult to determine on a streak plate. The hardness of corundum (9 on the Mohs scale) can also affect the accuracy of the streak test, as it can scratch the streak plate instead of leaving a distinct streak.
What is the color of corundum?
Corundum has no streak color. Because of being a clear white or light blue, its streak is actually clear.
Which minerals on the Mohs scale will not leave a streak on the streak plate?
Diamond, corundum, and hematite are three minerals on the Mohs hardness scale that will not leave a streak on the streak plate because they are harder than the streak plate itself.
What are 2 minerals that don't leave a streak on a streak plate?
Two minerals that do not leave a streak on a streak plate are quartz and fluorite. Both minerals have a hardness higher than that of the streak plate, so they will not leave a streak when rubbed against it.
Does the streak test work with all minerals?
No it does not work with all minerals. For if you did not know streak plates have a hardness of 7 (maybe a little lower or higher) on the Mohs scale. Some minerals are harder than 7 though. If they are harder they will not work with the streak test. some examples are Diamond, topaz, and corundum.
What is the plural of corundum?
Corundum.
Is corundum hexagonal or cubic?
Corundum ( (Al_2O_3) ) is hexagonal in crystal structure.
Which crystal system does corundum have?
Corundum is in the trigonal crystal system.
What are the eight ways to identify corundum?
Hardness: Corundum is one of the hardest minerals, scoring 9 on the Mohs scale. Color: Corundum can come in a variety of colors, with red corundum being called ruby, and all other colors referred to as sapphire. Crystal structure: Corundum typically forms in a hexagonal crystal structure. Luster: Corundum has a vitreous to adamantine luster. Transparency: It is commonly transparent to translucent. Cleavage: Corundum exhibits no cleavage, only conchoidal fracture. Specific gravity: Corundum has a specific gravity around 4.00. Refractive index: Its refractive index ranges from approximately 1.760 to 1.772.
What important uses does corundum have?
Corundum is used for jewlery
What do you call a red corundum?
Red corundum is called ruby.
