Diamonds
Diamond Simulants
Diamond's cleavage produces step-like breaks like the one
seen near the girdle of the round brilliant; a piece of glass
shows the smooth, curved fracture surface typical of simulants.
As is the case with most gem materials, diamond has various
physical and optical properties which can be measured very
precisely by a trained person with the right equipment. Here
are some of its important identifying properties and characteristics:
Optical:
- Refractive index (RI): 2.417
- Dispersion: .044
- Luster: adamantine
- Transparency: exceptional
Physical:
- Specific Gravity (SG): 3.52
- Hardness: 10 on Mohs scale
- Toughness: good in cleavage directions; otherwise exceptional
- Cleavage: four directions, perfect
- Fracture: step-like (alternating straight cleavages and
conchoidal fractures)
- Included crystals: angular ones are unique in type and
appearance
Cutting:
- Polish: superior (best possible)
- Facet edges: sharp (typically)
- Girdle: normally waxy to granular; bearding common
- Naturals: show characteristic growth markings
Other:
- Spectra: positive identifying absorption lines at 592,
504, 498, 478, 456, and 415 nm
- Wetability: difficult
- Thermal inertia: highest of any substance
- Response to X-rays: transparent; almost always fluoresces
blue
General Characteristics of Simulants
Although you can normally separate any diamond simulant from
diamond simply and reliably with the diamond thermal tester,
there are a number of other characteristics that expose various
simulants for what they are. Here are some of the more obvious
ones:
- All common diamond simulants (except some glass and some
doublets) have higher SGs than diamond.
- Only synthetic rutile, strontium titanate, and CZ have
significantly higher dispersion than diamond.
- Man-made stones may contain gas bubbles.
- Like diamonds, many common simulants do not give a reading
on standard refractometers (over the limits); but synthetic
sapphire, synthetic spinel, most glass, and some doublets
do.
- Synthetic rutile, zircon, and synthetic sapphire are doubly
refractive; diamond is singly refractive.
- Simulants with RIs below that of strontium titanate can
have a read-through effect.
|
