What is twinning in gemstone?
Scientifically, twinning occurs as gemstones are developing. The result is that their structure may be reflected, repeated incorrectly or rotated, resulting in the creation of a twin crystal that is attached to the original.
What is the streak of corundum?
Colorless
| Corundum | |
|---|---|
| Tenacity | Brittle |
| Mohs scale hardness | 9 (defining mineral) |
| Luster | Adamantine to vitreous |
| Streak | Colorless |
How is corundum formed?
Geology and Genesis of Metamorphic Corundum Deposits. Corundum is a high-temperature mineral that forms naturally by metamorphism of alumina-rich rocks under amphibolite and granulite facies conditions, and at temperatures between 500° and 800°C (Simonet et al., 2008).
Which type of inclusion can be a key identifying characteristic for gems such as ruby and sapphire?
Inclusions are among the most important features for identifying ruby and sapphire.
What is deformation twinning?
Deformation twinning is described by the twinning plane and a twinning direction. The shape of the twin is governed by the elastic strain which developes as it grows within the parent grain. The twin grows in a thin, sharply pointed plate as this minimises the elastic strain energy producing a lenticular shaped twin.
What causes twinning?
Dizygotic or fraternal twins form in the same way that all humans do, by the union of sperm and egg. The explanation for dizygotic twinning lies in the cause of hyperovulation, which is the release of more than one egg in a cycle of ovulation.
What is the chemical formula of corundum?
Al2O3
Corundum is an aluminum oxide mineral of the oxides and hydroxides group, with structural formula Al2O3.
How do you clean rough corundum?
How to Clean Rough Rubies
- Soak the rough ruby in lukewarm water.
- Remove the ruby from the soak.
- Choose a nonabrasive cleaner.
- Scrub the rough rubies using a soft bristled brush, sponge or towel.
- Rinse your rough ruby thoroughly.
- Store your rough ruby in a cloth-lined storage area separate from other jewelry.
What are the products that make use of corundum?
In addition to its use as a precious gem, corundum finds some use as an abrasive, owing to the extreme hardness of the material (9 on the Mohs hardness scale). It is used for grinding optical glass and for polishing metals and has also been made into sandpapers and grinding wheels.
What is the difference between corundum and sapphire?
Corundum is best known for its gem varieties, Ruby and Sapphire. Ruby and Sapphire are scientifically the same mineral, but just differ in color. Sapphire is also only used to describe the gem variety; otherwise it is simply called Corundum. Corundum is a very hard, tough, and stable mineral.
What is the difference between clear corundum blue sapphire and red ruby?
Scientifically speaking, rubies and sapphires are the same mineral (corundum). Both are made of alumina and oxygen, but they just differ in color. When a corundum is red, it is classified as a ruby, and when it’s blue, it is called a sapphire. Sapphires are blue when they contain traces of iron and titanium.
Is twinning a deformation mechanism?
Deformation twinning is another mechanism of plastic deformation. Like slip, deformation twinning enables a crystal to undergo a permanent shape change with negligible volume variation. Twinning occurs in adefinite crystallographic direction and on a specific crys- tallographic plane for each crystal structure.
Can deformation twins in cubic crystals be thickened by spontaneous nucleation?
The conclusion that thickening of deformation twins in cubic crystals by spontaneous nucleation of successive loops of twinning dislocation is not possible rests on the assumption that the interface region possesses the elastic properties of the matrix.
How does deformation temperature affect twinning in alloys?
Increase in deformation temperature above room temperature led to increased twinning in all alloys, and this was often manifested by the formation of thicker twins rather than by an increase in their number density.
What causes the twinning of crystals?
The interpretation of these results was that twinning is normally initiated by some defect configuration, but that in highly perfect crystals which deform at much higher stresses, homogeneous nucleation of twins may occur.
What is the Q value of deformation twinning?
As discussed in Section 2.7, the deformation twinning mode found experimentally for this plane is, most unusually, a q = 8 mode, whilst the displacement of the boundaries of the observed {1 OT 1} transformation twins may be regarded as a q = 4 mode.