Difference between revisions of "Synthetic moissanite"
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==Diagnostics== | ==Diagnostics== | ||
− | Synthetic moissanite can be easily separated from diamond by the doubling of facets, due to its high birefringence. Synthetic moissanite is usually cut with the table cut perpendicular to the optic axis, so care should be taken to observe the stone | + | Synthetic moissanite can be easily separated from diamond by the doubling of facets, due to its high birefringence. Synthetic moissanite is usually cut with the table cut perpendicular to the optic axis, so care should be taken to observe the stone from an angle to the table.<br /> |
Other clues are parallel needles (along the optic axis) and pinpoint inclusions in synth. moissanite. | Other clues are parallel needles (along the optic axis) and pinpoint inclusions in synth. moissanite. | ||
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===Specific gravity=== | ===Specific gravity=== | ||
− | The specific gravity of moissanite is lower than that of diamond and it will float in methylene iodide (SG = 3.33) while | + | The specific gravity of moissanite is lower than that of diamond and it will float in methylene iodide (SG = 3.33) while diamond will sink in it. |
===Magnification=== | ===Magnification=== | ||
− | The doubling of | + | The doubling of facets in facetted stones will easily separate synthetic moissanite from diamond.<br /> |
Typical inclusions include: | Typical inclusions include: | ||
* Parallel needles along the optic axis | * Parallel needles along the optic axis |
Revision as of 08:04, 31 August 2007
Synthetic Moissanite | |
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Chemical composition | Silicon Carbide - SiC |
Crystal system | Hexagonal |
Habit | Boule plates |
Cleavage | Weak (good parting) |
Fracture | Unknown |
Hardness | 9.25 |
Optic nature | Uniaxial + |
Refractive index | 2.648 - 2.691 |
Birefringence | 0.043 |
Dispersion | High, 0.104 |
Specific gravity | 3.22 |
Lustre | Sub-adamantine |
Pleochroism | Unknown |
Moissanite is a natural occurring mineral that is named after its discoverer, 1906 Nobel Prize (chemistry) winner Henri Moissan (1852-1907). As a natural source, this mineral is not suitable to be cut into gemstones as it occurs in too small grains.
Synthesizing moissanite has never been a real problem, however at first it was only synthesized for industrial purposes. This material, with a hardness of 9.25 on Moh's scale, is known by many bench jewelers and lapidarists as "carborundum" and is widely used as a sharpening tool for gravers and scrapers. As many who use carborundum can testify, this material is not very attractive as a gemstone.
Around 1987 Cree Research found a method to produce gemstone quality synthetic moissanite, but it was not until 1993 that a near-colorless crystal was obtained. Today this gemstone synthetic is marketed as Charles & Colvard created Moissanite™.
Although a nice synthetic on its own, this material is used mainly as a diamond simulant. Since the arrival of synthetic cubic zirconia in 1976, this is the most convincing diamond simulant, although a trained eye can easily separate synthetic moissanite from diamond.
Contents
Diagnostics
Synthetic moissanite can be easily separated from diamond by the doubling of facets, due to its high birefringence. Synthetic moissanite is usually cut with the table cut perpendicular to the optic axis, so care should be taken to observe the stone from an angle to the table.
Other clues are parallel needles (along the optic axis) and pinpoint inclusions in synth. moissanite.
Refractometer
Synthetic moissanite has a refractive index higher than diamond and the standard gemological refractometer will not be of any help.
The "dot test" will not help much either, but it will separate synthetic moissanite from zircon.
Specific gravity
The specific gravity of moissanite is lower than that of diamond and it will float in methylene iodide (SG = 3.33) while diamond will sink in it.
Magnification
The doubling of facets in facetted stones will easily separate synthetic moissanite from diamond.
Typical inclusions include:
- Parallel needles along the optic axis
- Pinpoint inclusions, often in clusters
Polariscope
Synthetic moissanite is uniaxial so it will show an anistropic reaction under crossed polars.
The interference pattern is uniaxial with a positive optic sign (like zircon).
References
- Synthetic moissanite: A new man-made jewel - Kurt Nassau, Current Science Vol 79 No 11, 10th Dec 2000 (Indian Academy of Science).