Khin’s Corner -
A Jewelry Appraiser’s Blog
Welcome to “Khin’s Corner – A Jewelry Appraiser’s Blog” and thanks for taking a moment to read this month’s Blog! Here is where we delve into all things related to your precious jewelry.
This month we’re learning about Simulated Diamonds.
Simulated diamonds, called simulants by professionals, differ greatly from natural diamonds and lab grown diamonds. How then do we differentiate the various types of stones that “look-like” diamond?
Before we explore differentiation, let’s look at some facts about simulants:
Simulants can be either natural or manufactured.
Simulants do NOT have the physical, chemical, or optical properties of a diamond.
Simulants mimic the appearance of diamonds.
Diamonds show sharpness on facet junctions (because of a diamond’s hardness, the facet junctions have clean, sharp angles on the edges of the facets), whereas simulants do not have the same strength and have rounded edges and easily show signs of wear with chips, scratches and abrasions.
Polished diamonds have higher luster than simulants.
Most simulants have a higher SG (specific gravity) which means that most simulants weigh more than diamond of the same size would weigh.
A diamond’s temperature remains cooler longer than a simulant because diamonds have higher thermal conductivity.
If a thermal tester (an instrument that measures heat conductivity) is used, care must be taken because a synthetic moissanite has similar thermal conductivity and may read as “diamond”.
Simulants have lower refractive index and a larger critical angle than a diamond, causing the light leakage through the pavilion which means you can see through round brilliant simulants.
Diamond has lower light dispersion (commonly called “fire”) than most simulants.
If chipped, diamonds get step-like fractures, whereas many simulants get curved (conchoidal) fractures.
A diamond has difficult “wettability”, which means a drop of water will form a bead on the surface of a diamond.
Diamonds and simulants can both have fluorescence, but the colors vary.
Various forms of simulants have different hardness ratings according to “MOHS ranking of hardness”. A diamond ranks the hardest at a score of 10 on MOHS scale. (See picture below for other rankings)
What are simulants made of?
Glass, also called “strass” or “paste” (this has been in use since the 1700’s)
Rhinestones also known as “foilbacks”
Garnet-and-glass Doublets (since around the 1840’s)
Flame-fusion simulants: colorless synthetic sapphire or spinel (since the 1800’s)
Natural colorless Zircon
Natural colorless Sapphire
Synthetic rutile (since 1948) also known by the fancy name of “Rainbow Magic Diamond”
Strontium Titanate (since 1953) also called “Diamontina”
YAG, which is Yttrium-Aluminum Garnet (since the 1960’s)
GGG, Gadolinium-Gallium Garnet (since the 1960’s)
Synthetic CZ or Cubic Zirconia (since the 1970’s). CZ’s are heavier than diamonds. CZ’s are sometimes called: Absolute, Diamonair, Diamonesque, Diamonesque III, Dimond nexus, Signity stone, or Diamantine.
Synthetic Moissanite (since the 1990’s). These are lighter than a real diamond and as mentioned earlier, some thermal testers can falsely read synthetic moissanite as “Diamond”.
The Process of Differentiation:
Natural diamonds and lab grown diamonds are almost impossible to tell apart with the naked eye; they have essentially the same chemical, physical, and optical properties. To tell the difference between natural and lab grown, the diamond must be examined by a trained and experienced gemologist with a well-equipped laboratory, such as the lab located at Good Khin Gems, LLC. The gemologist will run specialized testing, such as: UV (Ultraviolet) reaction to check for fluorescence and phosphorescence; CPF (Cross Polarized Filter); Raman Spectroscopy (which reveals information about the crystalline structure and molecular composition); and, additionally, microscopic analysis to check for the nature of inclusion, if one exists in the stone.
Identification of simulants in comparison to diamonds, however, can be performed with some less difficult methods. These include procedures such as: dispersion; read through effect; girdle luster; chips, luster, or sharpness on facet junction; doubling; laser inscription on girdle; and carat weight if the stone is unset.
If a “diamond tester” device is used to help identify whether a stone is natural, lab-grown, or simulant, caution must be taken because some stones can easily pass the tester and read as diamond. Other tests must be performed to confirm the identity of the stone.
If you have a stone and need it evaluated and/or appraised, it goes without saying that the best methods involved the right equipment, the experience, the background knowledge, and the trained eyes of the experts at Good Khin Gems, LLC.
The Birthstones for August are Peridot, Spinel and Sardonyx
(Those of you born in August get to enjoy 3 birthstones!)
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