Diffusion treatment consists of exposing the surface of a stone to certain chemicals combined with high heat in a furnace. Generally, only the surface color changes, so if you sliced the gem in half, the inside of the stone would be a different color, usually a paler, less valuable color.
What is gemstone dispersion?
When white light passes through a gemstone, each of its colors travels through it at a different speed. This is literally “dispersion” — the wavelengths previously joined in white light “disperse” and exit the gem separately, creating the rainbow color display. For example, blue is a short wavelength of light and travels slowly ...
What is gemstone diffusion treatment?
Jan 17, 2019 · Dispersion Chart. Some gems display flashes of light when held and turned it in the light, which is the result of the dispersion of white light into the separate spectral colors. Dispersion occurs when white light is separated into colour according to wavelength. Diamond is famed for this quality, but a number of other gemstones are notable for ...
How do gemologists measure the dispersion of gemstones?
Nov 08, 2018 · Diffusion treatment is a popular method for treating star sapphire, since the treatment will increase the asterism (the star effect in sapphire and ruby ). The diffusion process may reach a depth of half a millimeter into the gemstone. The process enhances the star effect on the gemstone and the stone can be sold as a diffused star sapphire.
Is there any controversy surrounding the method of treatment of gemstones?
The gemstone widely sold as “red andesine,” a material of questionable origin and marketed in prodigious quantities in recent years, presents a more egregious example of undisclosed treatment. Laboratory testing has confirmed that the red (and green) color seen in this product can be produced by diffusion of copper into pale, yellow-colored ...
What is gemstone dispersion?
What gemstone has the most dispersion?
Are treated gemstones less valuable?
Most people want to buy or wear an emerald but since an emerald costs $50K per carat (untreated), most people cannot afford it. The solution is a treated emerald that starts at $10 per carat and can go up to $10K per carat.May 24, 2019
What are some treatments used for gemstones?
- Bleaching. – a chemical used to alter / reduce a component of, or the entire color, of a porous gem. ...
- Surface Coating. ...
- Dyeing. ...
- Fracture or cavity filling. ...
- Heat Treatment. ...
- High pressure, high temperature (HPHT) treatment. ...
- Impregnation. ...
- Irradiation.
Does diamond have dispersion?
What is the dispersion of quartz?
Which gemstones are not treated?
- Spinel. Spinel is a historic gemstone with great colors and exceptional clarity and yet is underrated despite often being mistaken for valuable rubies. ...
- Peridot. ...
- Chrysoberyl. ...
- Tourmaline. ...
- Iolite. ...
- Andalusite. ...
- Chrome Diopside. ...
- Sunstone.
What is oiling in gemstones?
How can you tell if a gemstone is dyed?
How do you seal gemstones?
Are all gemstones treated?
How can I improve my gemstones?
The most common form of enhancement is heating. For example, jewelers should inform their customers that rubies and sapphires are “probably heat treated,” since heating is so common for corundum gems. Heat-treated ruby.
What is the measurement of dispersion?
Dispersion can be measured with a refractometer. Dispersion is usually expressed numerically as the difference between the red and violet refractive indices. In the following chart, the values for dispersion represent the difference between the red and violet refractive indices, which are known as the BG Fraunhofer lines.
What is the dispersion of light?
Dispersion Chart. Some gems display flashes of light when held and turned it in the light , which is the result of the dispersion of white light into the separate spectral colors. Dispersion occurs when white light is separated into colour according to wavelength. Diamond is famed for this quality, but a number of other gemstones are notable ...
What is green quartz?
Green quartz is properly known as prasiolite. Further heating of these gems causes a complete loss of color. Irradiation plus heating may also produce brown, orange, and yellow hues in quartz. The heating of amethyst to a brownish yellow color occurs on a commercial scale.
What color does tourmaline turn?
Heating usually lightens the color of tourmaline but can also sometimes turn a dark green stone an attractive, emerald-like color. Gamma irradiation of tourmaline produces spectacular color changes. Pale pink and some colorless stones may turn dark pink.
How is black onyx made?
“Black onyx” is made by soaking grayish colored chalcedony in a sugar solution and then blackening in sulfuric acid. This process leaves very tiny particles of carbon in the pore spaces of the chalcedony.
Is topaz a color?
Topaz, for example, occurs in various colors. Pale blue topaz isn’t uncommon, but deep, intense blue stones don’t occur in nature. However, gamma irradiation of certain colorless topaz can produce such gems. This treatment turns the material greenish brown, but then heating produces a rich blue color. Some golden or yellow topaz can be heated to yield a pink or purplish red color.
Is blue topaz rare?
Pale blue topaz isn’t uncommon, but deep, intense blue stones don’t occur in nature . However, gamma irradiation of certain colorless topaz can produce such gems. This treatment turns the material greenish brown, but then heating produces a rich blue color.
What color is Tanzanite?
Heating certain crystals, which eliminates the red-violet color component, produces the lively sapphire-blue color that has made the gem so popular.
How rare is aquamarine?
Dark blue aquamarine is quite rare and very costly. Many of the dark stones seen in jewelry are produced by heating greenish or brownish material to a temperature of 400-450°C. The treatment results in a permanent color change.
Basic
Dispersion is the splitting up of white light into its individual wavelengths, what we see as colors. Dispersion occurs with transparent surfaces that are not parallel to each other, such as gemstone facets.
Advanced
Measurement of dispersion is usually carried out using a table spectrometer. Through the minimum deviation method, very accurate refraction indices can be obtained with this apparatus (more accurate than with the refractometer). This type of instrument can be obtained for around USD 1500.00, and takes some skill to operate.
General Information
Prasiolite is a type II clarity stone. Stones may contain crystals, negative crystals, liquid inclusions, two-phase inclusions and partially-healed fractures.
Countries of Origin
Tanzania, United Republic Of; United States of America (the); Uruguay; Madagascar; Thailand; Bolivia (Plurinational State of); India; Mozambique; Unknown; China; Brazil; Mexico; Zimbabwe
History
Prasiolite is an easy-going, gentle, pastel-green stone. Although it's found naturally, it's extremely rare. So... we nudge Mother Nature! As with many stones, heat treatments are transforming. Amethyst from Montezuma, Minas Gerais, Brazil was first found to turn green when it was heated.
More About Prasiolite
One of the folkloric attributes of prasiolite is that it fosters compassion. Those who believe in the powers of gemstones say that this stone encourages self-acceptance and self-honor, that it ignites love and brings spiritual ideals into everyday life. Embrace its easy and enviable green.
