5 - Treatments, Lab-Grown, Imitations, and Disclosure Flashcards
Treatment
Any human-controlled process outside of cutting or polishing that improves the appearance, durability, or value of a gem.
Diamond Bourses
Where dealers meet to exchange goods.
Disclosure
Clearly and accurately informing customers about the nature of the goods they buy.
What are the ten types of gem treatments?
Bleaching
Cavity Filling
Colorless Impregnation
Dyeing
Fracture Filling
Heating
Irradiation
Lattice Diffusion
Sugar & smoke treatments
Surface modification
Bleaching
A treatment that uses chemicals to lighten or remove color.
Which two organic gems commonly undergo bleaching, and what bleach is commonly used?
Pearls and ivory, with hydrogen peroxide.
What three gems are commonly bleached and what is used?
Tiger’s eye, jadeite, chalcedony, with diluted acid and chlorine bleach.
How can bleaching be used to lighten inclusions?
Laser-drilling and stronger solvents.
Cavity filling
Fills and seals voids to improve appearance and add weight.
What kind of blemishes does cavity filling address?
Cavities, pits, and other depressions.
What kind of fillers are typically used in cavity filling?
Glass, plastic, and shellac.
In what four gems is cavity filling frequently seen?
Tourmaline, opal, ruby, sapphire.
What aspect of durability and what aspect of appearance does cavity filling improve?
Durability - hardness; appearance - luster.
Colorless impregnation
Filling of pores or other openings with melted wax, resin, polymer, or plastic to improve appearance and stability.
What kind of materials are often used in colorless impregnation?
Wax, resin, polymer, and plastic.
What are the benefits of colorless impregnation?
Can seal, protect, and improve luster.
What two gems are commonly treated with colorless impregnation?
Turquoise, jadeite.
Dyeing
Adds or affects color by making it more even or changing it.
What is required before a gem can be dyed?
A gem must have a porous surface or fractures that reach the surface.
Quench-crackling
When a gem is rapidly heated and cooled to produce surface fractures, in order to prepare for dyeing.
What five gems are typically dyed?
Turquoise, cultured pearl, chalcedony, lapis lazuli, jadeite.
How can rock crystal be treated to imitate gems?
Rock crystal can be quench-crackled.
Fracture (fissure) filling
Using a filler to conceal fractures and improve the apparent clarity of a gem.
What materials are used in fracture filling?
Plastic, glass, polymer resins, and oil (Canada balsam and palm oils).
In what gem is fracture filling most common?
Emerald
How is ruby typically fracture-filled?
Ruby in particular is treated with high-lead-content glass.
Heat treatment
Exposing a gem to rising temperatures for the purpose of changing its appearance.
Is heat treatment stable?
Yes, under normal wear.
How can heat treatment affect a near-colorless corundum?
It gives a blue color.
How can heat treatment affect a dark blue sapphire?
It can lighten or eliminate blue.
How can heat treatment affect rubies?
It can remove the purplish hue that some rubies have.
How can heat treatment affect amber?
It can oxidize it and sometimes remove bubbles.
Give an example of how heat treatment can add helpful inclusions?
It can create asterism.
What is the usual length of treatment and chemical used?
It varies based on the desired result.
What three elements cause a blue color in lattice diffusion?
Iron, titanium, beryllium.
What two elements cause a red color in lattice diffusion?
Chromium, beryllium.
What element and process causes blue asterism with lattice diffusion?
Titanium dioxide and long cooling.
What colors can beryllium induce in lattice diffusion?
Pinkish orange, yellow, red, blue.
Sugar treatment
Soaking an opal in hot sugar solution and then in sulfuric acid to darken it and bring out play-of-color.
Smoke treatment
Heating a wrapped, usually low-grade opal until smoke or ash penetrates the surface to darken it and bring out play-of-color.
What two things do sugar and smoke treatments have in common?
They are both surface treatments, and they both work based on carbon entering the stone.
Surface modification
Altering the appearance by applying backings, coatings, or coloring agents (i.e. paint.)
Backing
Applied to the pavilion, usually silver/gold foil, fabric, paper, or colored feathers.
Where are backings usually used?
Costume jewelry
What are the five usual types of coatings?
Wax, varnish, plastic, ink, and metallic compounds.
What type of coating improves the luster of turquoise, jadeite, lapis lazuli, and opal?
Wax
What are four types of gemstones that sometimes take coatings other than wax?
Beryl, corundum, quartz, jadeite.
What are the compounds used for coloring agents?
Paint, ink, nail polish.
What was the initial use of lattice diffusion?
Originally used to create asterism in sapphires.
What are some popularly treated gems? Try to name 10.
Amethyst
Aquamarine
Chalcedony
Citrine
Emerald
Jade
Lapis Lazuli
Opal
Pearl
Ruby
Sapphire
Tanzanite
Tiger’s-eye
Topaz
Turquoise
Zircon
What is considered a permanent treatment?
Some heat treatments.
How difficult is it to detect heat and irradiation?
Very.
What light feature is a strong indication of treatment?
Extraordinary color.
Describe irradiation’s vulnerabilities.
Can fade quickly in light in any kind, can destabilize with heat.
Describe dyeing’s vulnerabilities.
Can fade in sun and burn in heat.
Describe colorless impregnation’s vulnerabilities.
Wax or oil can “sweat” in heat, oils can dry up, standard cleaning can remove treatment.
Describe the vulnerabilities of bleaching.
Does not hold up against chemicals that stain, can include skin oils.
Describe the vulnerabilities of surface treatments.
Standard cleaning can remove treatments, heat can vaporize them.
What is a common disruptor of treatments?
Heat
Flame fusion
Powdered chemicals are dropped through a high-temperature flame onto a rotation pedestal to produce a synthetic crystal.
Who pioneered flame fusion?
Verneuil
What is the most common and least expensive method of growing synthetic stones?
Flame fusion
Pulling
The synthetic crystal is grown from a seed that is dipped in chemical melt, then pulled away as it gathers material.
Flux growth
Nutrients dissolve in heated chemicals, then cool to form synthetic crystals.
Hydrothermal growth
Nutrients dissolve in a water solution at high temperature and pressure, then cool to form synthetic crystals.
How do new synthetic gemstone methods affect the market of natural gems?
It tends to increase interest in the natural gemstone.
Imitation gem
Any material that looks like a natural gem and is used in its place.
What are natural look-alikes?
Other natural gemstones of the same color (i.e. green garnet = emerald)
What are lab-grown imitations?
Lab-grown gemstones that are not necessarily the same chemical composition and crystal structure (i.e. lab-grown spinel for birthstones)
What are plastic imitations?
Thoroughly unconvincing plastic replicas.
Assembled stones
Fusion of 2+ separate pieces of material for a single piece.
Doublet
Two separate pieces of material fused or cemented together to become a single assembled stone.
Triplet
A single assembled stone formed from three pieces of material fused or cemented, or from two pieces and a colored cement layer.
Phenomenal imitations
Manmade processes that can imitate phenomena in non-gems (ex. Cat’s-eye glass)
Does the FTC care when you cry?
No
When should you disclose treatments?
Always, along with the 4 Cs.
