GEM ENHANCEMENTS & CARE
Jewels have been objects of desire from the earliest days of mankind. The enduring value of gems and pearls is largely a result of their beauty, durability and rarity. It is this last aspect that has pushed humans to create less expensive alternatives to the natural product. These include imitations such as glass, fully synthetic counterparts of natural gems and enhancements that modify gems and pearls to make them more valuable.
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| Tanzanite is a gem that would not be available in commercial quantities if it wasn't heat treated |
Certain enhancements have been practised for literally thousands of years. The dying of agate is one example. Others, such as irradiated blue topaz, are solely a product of the technological advances of the modern age.
Enhancements have a definite impact on the value of precious stones, with the highest prices paid for natural gems of fine quality that have not been enhanced in any way beyond ordinary cutting and polishing. As a gem is modified to a greater and greater degree, the change in value is also greater. The least expensive gems are those fully made by man (synthetics), because the supply is essentially unlimited. Thus they have limited or no rarity.
What follows is a comprehensive description and discussion of enhancements.
Enhancement disclosure
GemsTV takes enhancement disclosure seriously and, to the best of our ability, provides our clients with complete information on any and all enhancements to which a gem has been subjected. The descriptions we provide below are based upon those of the American Gem Trade Association guidelines (the most stringent in the industry). While many enhancements are currently undetectable, GemsTV does its best to ensure that clients have full access to information for an informed buying decision.
- GemsTV discloses all known enhancements at the time of sale and backs this up with a 30-day return policy.
- For most gems today, enhancements are a basic part of the finishing process.
- While unenhanced gems are the most sought-after, their tremendous rarity and, thus, high prices, put them out of reach of all but the wealthiest of buyers.
- In order to provide beautiful jewellery to our full spectrum of customers, we offer a broad selection of enhanced gems, in addition to our lines of unenhanced precious stones.
- The marketplace sets the values of both natural and enhanced gems.
Since certain enhancements are undetectable or difficult to detect, the GemsTV approach is to assume that all items are enhanced unless:
- There is specific gemological evidence that shows the item has not been enhanced.
- The item is of a type for which enhancements are not typically used.
We do our best to describe our gems in a clear, consistent and honest fashion. Our approach is to give our customers the same information we would like if we were purchasing the piece. Our mantra is to be true both to our customers and to the precious stones with which we are privileged to work.
Definitions
The term enhancement describes any process other than ordinary cutting and polishing that improves the appearance, durability or value of an otherwise natural gemstone or cultured pearl. In today's gem marketplace, enhanced gems are the rule rather than the exception. Such processes range from simple heating (such as with tanzanite) to high-tech irradiation (such as with blue topaz).
Note that an enhancement is, by definition, an artificial process, since it involves human intervention. Thus using a "natural" cedarwood oil to enhance an emerald does not make the process more "natural."
There exist several categories of gems, as follows:
- Fully natural: Stones produced by simply obtaining the raw gem material in nature, cleaning it and then cutting and polishing. With the exception of cleaning and ordinary cutting and polishing, natural gems are fully natural. Examples include natural garnet and peridot.
- Natural, but enhanced: Stones produced by obtaining the raw gem material in nature, but then processing it in any way beyond normal cleaning, cutting and polishing. Examples include heat-treated sapphire, tanzanite and paraíba tourmaline.
- Synthetic: Man-made analogs of natural gem materials. In order to qualify as a synthetic, the man-made product must have the same appearance, chemical composition and structure as its natural counterpart. Examples include synthetic ruby and synthetic emerald.
- Imitation: A gem that has the same appearance as another gem. There are infinite possibilities, including both natural and man-made imitations. Thus natural iolite might imitate a heated tanzanite, while man-made glass might also do the same.
- Assembled: These are gems made of two or more pieces put together. The pieces can be any combination of natural, synthetic or treated gems. They may be assembled with glue, pressure or even by fusing one piece to another with heat. Examples include opal doublets and triplets and garnet-and-glass doublets.
It should be noted that enhancements are not limited to natural gems. They may also be applied to man-made products.
Estimated degree of enhancement
In order to give an estimate of the degree of alteration that a gem has undergone via enhancement, we have created an Estimated Degree of Enhancement Scale. This gives the buyer an idea about the quality of rough prior to treatment. Some processes only lightly enhance a gem, while others have a more significant impact. We use the following scale:

Frequency used
This represents a reasonable estimate of how commonly a particular enhancement process is utilised in the trade, based on a consensus of opinion. GemsTV rates this on the following scale:
|
Common |
Occasional |
Rare |
Stability
Some enhancements are less stable than others, meaning that the appearance of a gem may change with time. GemsTV rates stability on the following scale:
|
Good |
Fair |
Poor |
In the event that a gem with less than good stability is offered, GemsTV does their best to make clients aware of the special care needed for that stone. An enhancement is considered stable as long as the gem does not change in appearance or stability under normal wear, cutting, cleaning, repair, or display conditions.
Care required
This relates to special care that may be necessary to preserve the effect of the enhancement and/or to preserve the overall look and integrity of the gem. GemsTV rates this on the following scale:
|
Normal |
Care Needed |
Special Caution |
Special advice
This addresses the need for any special care required by the specific gemstone variety, irrespective of enhancement.
Enhancement categories
The following table shows the enhancements and treatments used for some popular gemstones, their purpose, frequency and care.
- Natural (N)
Gems that are, according to best available information, untreated. - Enhanced (E)
Gems that are treated.
Codes for specific forms of enhancement
GemsTV does not simply state that a gem has been enhanced, but also tries to give specific information about the enhancement type, according to the following codes:
Heat
- H = Heat Only: Alteration via heat only (or heat + hydrogen). Example: Heated ruby, heated sapphire, heated tanzanite
- HD = Heat + Diffusion (aka 'bulk' or 'lattice' diffusion): Alteration via heat and outside-in diffusion of foreign elements other than hydrogen. Example: Beryllium-diffused sapphire
- HF = Heat + Flux: Alteration via heat and flux. During heating, fluxes dissolve surface-reaching fissure walls and redeposit that dissolved gem material, healing the fissures closed. Example: Flux-healed ruby (particularly that from Möng Hsu, Burma)
- HI = Heat + Irradation: Alteration of color via the use of neutrons, gamma, ultraviolet and/or electron bombardment, followed by heating. Example: Irradiated blue topaz
- HP = Heat + Pressure: Alteration via heat and pressure. Example: HPHT diamond
Filling
- F = Filling: Impregnation with a colorless substance. This is typically done to improve clarity, but also improves color, as clarity enhancement facilitates longer light paths within the gem. Fillers include but are not limited to glass, plastic, resin, wax and oil. Some fillers remain fluid at room temperature (and thus are less stable), while others are hardened. Note that any gem with the requisite openings can be filled. Example: Oiled emerald, glass-filled ruby, stabilised turquoise
- FD = Filling + Dye: Impregnation with a colored filler, typically done to add or improve color and possibly also clarity. Note that any gem with the requisite openings can be dyed. Example: Dyed green jadeite
Irradiation
- I = Irradiation: Alteration of color via the use of neutrons, gamma, ultraviolet and/or electron bombardment. Example: Irradiated morganite
Coating
- C = Coating: Application of an artificial layer to the surface. Example: Coated diamond, coated topaz
Bleaching
- B = Bleaching: The use of heat, light and/or chemical agents to lighten or remove color. Subsequent dying and/or filling often accompany this. Example: Bleached cultured pearl, bleached/filled jadeite ('B-jade')
Laser Drilling
- L = Laser Drilling: Use of a laser and chemicals to reach and alter inclusions. Example: Laser-drilled diamond
Reconstruction
- R = Reconstruction: Use of heat, pressure and/or solvents to fuse small pieces of a gem together into a larger whole. Example: Reconstructed amber
Further notes
- Note that gems may be enhanced by more than one process.
- The presence or absence of enhancements can have a significant impact on value. Thus it is always a good idea to have major purchases tested by a well-respected gemological lab.
Caring for your gemstone jewellery
Gems are among the most durable of nature's creations, but still require care if they are to retain their beauty. Caring for your jewellery is a matter of common sense and simple precaution:
- Always remove your jewellery when engaging in activities that risk impact or exposure to chemicals or heat such as sports or housework.
- Always put jewellery on after using lotions, cosmetics, hair spray or perfumes, not before.
- Never remove your jewellery by pulling on the gems.
- The best way to store your jewellery is in the compartments of a jewellery box or in pouches. Store each piece of gemstone jewellery separately and necklaces flat so that harder stones don't scratch softer ones. Almost every gem is harder than the metal in which it is set. Gems can scratch one another or the finish on your jewellery if stored carelessly.
- Carefully wipe jewellery with a soft lint-free cloth after each wearing to remove oils and salts.
- Clean your jewellery on occasion with a cleaning solution or mechanical cleaner suitable for the gem; use a dish rather than the sink, for if a gem accidentally falls out of the setting, down the drain it goes. When in doubt, just use warm soapy water and a soft toothbrush.
- Think twice before putting gems in an ultrasonic cleaner. Diamonds and rubies and sapphires are generally fine but many other gems may not be. Thus when in doubt, leave it out.
- Opaque gems such as lapis lazuli, turquoise and malachite can be porous and may absorb chemicals and soap, discoloring them. Thus they require special care. Never use ultrasonic cleaners, ammonia or chemical solutions. These gem materials should just be wiped clean gently with a moist cloth.
- Opals also require special care. Never use an ultrasonic, never use ammonia, and avoid heat and strong light that can dry out the water in opals.
- Organic gems like pearls, coral and amber should only be wiped clean with a moist cloth. Due to their organic nature, these gems are both soft and porous. Be careful about chemicals in hairspray, cosmetics, or perfume; over time they can damage pearls in particular.
- Stones that have a Mohs hardness of 7 or less are subject to scratching; harder stones are less susceptible, but still subject to chipping and fracture.
For complete care instructions on each gem type, please see the tables below.
Mechanical cleaners
The most common mechanical cleaners are ultrasonic and steam cleaners. Ultrasonic cleaners feature two basic parts: a small motor and a cleaning tank. The machine's motor produces ultrasonic energy that is transmitted with vibrating energy waves (usually 40,000 sound waves per second) to create microscopic bubbles in the cleaning tank. Called cavitation, this motion knocks dirt off the jewellery and is very effective in penetrating the tiny crevices in jewellery that traditional cleaning cloths and topical cleaners cannot easily reach. A steam cleaner uses jets of steam to literally blast dirt off jewellery. As mechanical cleaners can damage some gemstones, always check to see if your gemstone is suitable.
Final notes
The following tables show the enhancements used for both major and minor gems, along with care instructions. This has been compiled based on our own experience, coupled with the expertise of our suppliers, the world's major gemological laboratories, trade associations, regulatory bodies, professional journals, etc. These tables include all known enhancements, even those not applied to the gems sold by Thaigem.com.
Note that enhancements are constantly being developed and altered. We do our best to provide the latest information, but if there are questions, the best solution is to have the individual gem tested by a major gemological laboratory.
Gem Enhancement & Care Chart - Normal Gems
Gemstone |
Hardness |
Code & Degree |
Enhancement Method |
Frequency Used |
Stability |
Care Required |
Special Advice |
|---|---|---|---|---|---|---|---|
| Agate (see Quartz-Chalcedony) |
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| Alexandrite (see Chrysoberyl) |
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| Amazonite (see Feldspar) |
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| Amber | 2-2.5 | The skin of amber may naturally darken with age. Thus repolishing may produce a lightening of color. | |||||
| All varieties | H/L | Heated to improve appearance | Common | Good | Care needed | Avoid heat, steaming, chemicals and ultrasonic | |
| FD/S | Dyed to improve appearance | Rare | Variable | Care needed | Avoid repolishing, heat, steaming, chemicals and ultrasonic | ||
| R/S | Heated under pressure to fuse small pieces into a larger piece | Common | Good | Care needed | Avoid heat, steaming, chemicals and ultrasonic | ||
| Green | HP/S | Heated under pressure to induce a green color | Common | Good | Care needed | Avoid heat, steaming, chemicals and ultrasonic | |
| Amblygonite / Montebrasite | 5.5-6 | I | Irradiated to improve color | Common | Good to Fair | Care needed | May be prone to thermal shock; avoid extreme temperature changes |
| Amethyst (see Quartz) |
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| Ametrine (see Quartz) |
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| Ammolite | 4 | ||||||
| All varieties | F/M | Impregnated with colorless hardened filler to improve appearance and durability | Common | Good to Fair | Care needed | Avoid heat, steaming, chemicals and ultrasonic; may not be suitable for re-cutting or re-polishing | |
| Andesine (see Feldspar) |
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| Andalusite | 6.5-7.5 | N | None | - | - | Care needed | Avoid boiling and ultrasonic cleaning |
| Apatite | 5 | H/L | Heated to improve appearance | Common | Good | Care needed | Avoid heat, steaming, chemicals and ultrasonic; somewhat soft; brittle; handle with care |
| Aquamarine (see Beryl) |
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| Aventurine (see Quartz) |
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| Azurite (includes Azurmalachite) | 3.5-4 | ||||||
| All varieties except druzy | F/L-M | Dipped in colorless wax to improve appearance; impregnated with colorless hardened or unhardened filler to improve appearance and durability | Common | Good to Fair | Care needed | Avoid heat, steaming, chemicals and ultrasonic | |
| Druzy | N | None | - | Good | Care needed | Brittle; avoid shock | |
| Beryl | 7.5-8 | ||||||
| Aquamarine | H/L | Heated to improve color | Common | Good | Care needed | Avoid sudden temperature changes, heat, steaming, chemicals and ultrasonic | |
| Blue ('maxixe' type) |
I/S | Irradiated blue from pale pink to colorless | Always | Poor | Special caution | Color fades; avoid light and heat | |
| Colorless (aka 'fire' or 'goshenite') |
N | None | - | - | Care needed | Avoid sudden temperature changes, heat, steaming, chemicals and ultrasonic | |
| Emerald | F/L-M | Impregnated with colorless hardened or unhardened filler to improve appearance | Common | Fair | Care needed | Avoid sudden temperature changes, heat, steaming, chemicals and ultrasonic | |
| FD/L-S | Dyed with hardened or unhardened filler to improve appearance | Occasional | Fair | Care needed | Avoid sudden temperature changes, heat, steaming, chemicals and ultrasonic | ||
| Pink (aka 'morganite') |
I + H/L | Irradiation followed by heating to improve color | Common | Good | Care needed | Avoid sudden temperature changes, heat, steaming, chemicals and ultrasonic; rarely may fade in light or heat | |
| Red emerald (aka 'bixbite') |
F/L-S | Impregnated with colorless hardened or unhardened filler to improve appearance | Common | Fair | Care needed | Avoid sudden temperature changes, heat, steaming, chemicals and ultrasonic | |
| Yellow & golden (aka 'heliodor'), green beryl |
I/M | Irradiated to improve color | Common | Variable | Care needed | Certain stones may fade in light or heat | |
| Bixbite (see Beryl) |
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| Bloodstone (see Quartz-Chalcedony) |
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| Brazilianite | 5.5 | N | None | - | - | Care needed | Fragile; handle with care; avoid heat, steaming, chemicals and ultrasonic |
| Carnelian (see Quartz-Chalcedony) |
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| Chalcedony (see Quartz-Chalcedony) |
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| Charoite | 5-6 | N | None | - | - | Care needed | Avoid heat, steaming, chemicals and ultrasonic |
| Chrysoberyl | 8.5 | ||||||
| Alexandrite | F/L-M | Impregnated with colorless filler to improve appearance | Rare | Fair | Care needed | Avoid sudden temperature changes, heat, steaming, chemicals and ultrasonic | |
| Cat 's eye | I/S | Irradiated to improve color | Rare | Good | Special caution | If neutron irradiated, refer to the NRC for safety requirements | |
| Chrysocolla | 2-4 (or more, if mixed with quartz) | F/M-S | Impregnated with colorless filler to improve appearance and durability | Common | Fair | Care needed | Avoid heat, steaming, chemicals and ultrasonic |
| Chrysoprase (see Quartz-Chalcedony) |
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| Citrine (see Quartz) |
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| Clinohumite | 6 | N | None | - | - | Normal | - |
| Coral | 3.5-4 | ||||||
| Black | N | None | - | - | Care needed | Avoid heat, steaming, chemicals and ultrasonic | |
| White | B/L | Bleached to improve appearance | Common | Fair | Care needed | Avoid heat, steaming, chemicals and ultrasonic; may discolor over time | |
| Pink, orange | F/L | Impregnated with colorless filler to improve appearance and durability | Common | Fair | Care needed | Avoid heat, steaming, chemicals and ultrasonic | |
| Red | FD/M-S | Dyed to improve appearance | Common | Fair | Care needed | May fade in light or heat; avoid heat, steaming, chemicals and ultrasonic | |
| Gold | B/S | Bleached from black coral | Common | Good | Care needed | Avoid heat, steaming, chemicals and ultrasonic | |
| Corundum | 9 | ||||||
| Ruby and sapphire of all types | H/L-S | Heated to improve appearance | Common | Good | Normal | - | |
| HF/M-S | Heated with flux to improve appearance and durability | Common | Good | Normal | - | ||
| HD/S | Heated with elements other than hydrogen to improve color and/or add asterism | Common | Good | Normal | If diffused layer is just at the surface, avoid repolishing | ||
| F/M-S | Surface pits filled with colorless hardened filler to improve appearance and/or add weight | Occasional | Fair | Care needed | Avoid heat, steaming, chemicals and ultrasonic | ||
| FD/S | Dyed to improve appearance | Rare | Fair | Care needed | Avoid heat, steaming, chemicals and ultrasonic | ||
| Ruby (aka 'majestic ruby') | FD/S | Impregnated with colorless or colored lead glass filler to improve appearance; sometimes classified as composite gemstones, these rubies are treated using heat and a high refractive index lead-glass to fill fractures and cavities. This vastly improves the apparent clarity and potentially adds weight and/or intensifies color and/or color uniformity and/or appearance. The lead-glass is typically yellow to orange in color and can artificially augment the red color of these gems. | Common | Fair | Care needed | Avoid heat, steaming, chemicals and ultrasonic. Fillers in cavities and/or fissures can scratch more easily than the host gem or be more vulnerable to damage from heat or some chemicals. The lead glass may be damaged by a variety of solvents. | |
| Yellow and orange sapphire | I/S | Irradiated to alter color | Rare | Poor | Care needed | Color fades with exposure to light and/or heat | |
| Danburite | 7-7.5 | ||||||
| Colorless, pink, yellow | N | None | - | - | Normal | - | |
| Brown | I/S | Irradiated to improve color | Common | Unknown | Care needed | May fade; avoid prolonged exposure to heat and light | |
| Diamond | 10 | ||||||
| All varieties | L/M | Laser drilled to improve appearance | Occasional to Common | Good | Normal | - | |
| C/S | Coated to improve appearance | Occasional | Good to Poor, depending on method | Special caution | Recutting, steaming, ultrasonic and occasionally alcohol may adversely affect color and appearance | ||
| F/S | Impregnated with hardened colorless filler to improve appearance | Occasional | Good | Care needed | Recutting, steaming, ultrasonic or extreme heat may remove filler | ||
| HP/S | Heated under pressure to improve appearance | Rare | Good | Normal | Recutting or extreme heat may remove filler | ||
| I/S | Irradiated and/or heated to induce fancy colors | Common | Good | Normal, except green | Avoid heating irradiated green stones as the color may change; some green stones have been radium irradiated; for safety requirements, refer to the NRC | ||
| C/S | Coated to produce fancy colors | Rare | Fair to Poor | Care needed | Recutting or extreme heat may damage coating | ||
| Diaspore | 6.5-7 | ||||||
| Zultanite | N | None | - | - | Care needed | Avoid heat, steaming, chemicals and ultrasonic | |
| Diopside | 5.5-6.5 | ||||||
| Chrome, star, cat's eye | N | None | - | - | Care needed | Avoid heat, steaming, chemicals and ultrasonic | |
| Emerald (see Beryl) |
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| Enstatite | 5-6 | N | None | - | - | Care needed | Avoid heat, steaming, chemicals and ultrasonic |
| Epidote | 6-7 | N | None | - | - | Care needed | Avoid heat, steaming, chemicals and ultrasonic |
| Euclase | 7.5 | N | None | - | - | Care needed | Brittle; avoid heat, steaming, chemicals and ultrasonic |
| Feldspar | 6 | ||||||
| Microcline (aka 'amazonite') | F/M | Impregnated with colorless hardened or unhardened filler to improve appearance | Common | Good to Fair | Care needed | Avoid heat, steaming, chemicals and ultrasonic | |
| Andesine (aka 'sunstone') | HD/S | Heated with Cu to improve appearance | Common | Good to Fair | Care needed | Avoid heat, steaming, chemicals and ultrasonic | |
| Labradorite (aka 'sunstone') | HD/S | Heated with Cu to improve appearance | Common | Good | Care needed | Avoid heat, steaming, chemicals and ultrasonic | |
| Labradorite (aka 'spectrolite') | F/M | Impregnated with colorless hardened or unhardened filler to improve appearance | Occasional | Good to Fair | Care needed | Avoid heat, steaming, chemicals and ultrasonic | |
| Labradorite (aka 'Oregon sunstone') | N | None | - | - | Care needed | Avoid heat, steaming, chemicals and ultrasonic | |
| Orthoclase (aka 'moonstone') | N | None | - | - | Care needed | Avoid heat, steaming, chemicals and ultrasonic | |
| Oligoclase (aka 'sunstone') | N | None | - | - | Care needed | Avoid heat, steaming, chemicals and ultrasonic | |
| Fluorite | 4 | ||||||
| I/M | Irradiated to improve color | Common | Fair | Care needed | Both naturally colored and irradiated fluorites may fade upon prolonged exposure to light; soft and brittle; handle with care; avoid heat, steaming, chemicals and ultrasonic | ||
| Gahnite (see Spinel) |
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| Garnet | 6.5-7.5 | ||||||
| All types except demantoid | N | None | - | - | Care needed | Avoid sudden temperature changes; avoid heat, steaming, chemicals and ultrasonic | |
| Demantoid | H/L | Heated to improve color | Common | Good | Care needed | Avoid sudden temperature changes; avoid heat, steaming, chemicals and ultrasonic | |
| Heliodor (see Beryl) |
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| Hematite | 5-6.5 | N | None | - | - | Care needed | Brittle |
| Hiddenite (see Spodumene) |
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| Idocrase (see Vesuvianite) |
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| Iolite (aka 'Tanolite' or 'Cordierite') | 7-7.5 | N | None | - | - | Care needed | Avoid thermal shock; damaged by acids |
| Ivory & Bone | |||||||
| All varieties | B/L | Bleached to whiten and remove discoloration | Common | Good | Care needed | Avoid heat, steaming, chemicals and ultrasonic; may discolor over time | |
| FD/M-S | Dyed to improve appearance | Occasional | Good | Care needed | Avoid heat, steaming, chemicals and ultrasonic; may discolor over time | ||
| F/M-S | Impregnated with colorless hardened or unhardened filler to improve appearance | Occasional | Good | Care needed | Avoid heat, steaming, chemicals and ultrasonic; may discolor over time | ||
| B + F/M-S | Two-step bleaching and colorless impregnation to improve appearance | Common | Good to Fair | Care needed | Avoid heat, steaming, chemicals and ultrasonic; may discolor over time | ||
| B + FD/S | Two-step bleaching and dying to improve appearance | Common | Good to Fair | Care needed | Avoid heat, steaming, chemicals and ultrasonic; may fade with time | ||
| FD/S | Dyed to improve appearance; dye may be selective in coverage | Common | Good to Fair | Care needed | Avoid heat, steaming, chemicals and ultrasonic; may fade with time | ||
| H/L | Heated to intensify brown/orange color | Common | Good | Care needed | Avoid heat, steaming, chemicals and ultrasonic | ||
| H/L | Heated with or without chemicals to simulate age | Occasional | Good | Care needed | Avoid heat, steaming, chemicals and ultrasonic | ||
| Jadeite Jade | 6.5-7 | ||||||
| All varieties | F/L | Dipped in colorless wax to improve appearance | Always | Fair | Care needed | Avoid heat, steaming, chemicals and ultrasonic | |
| B + F/S | Two-step bleaching and colorless impregnation to improve appearance | Common | Good to Fair | Care needed | Avoid heat, steaming, chemicals and ultrasonic | ||
| B + FD/S | Two-step bleaching and dying to improve appearance | Common | Good to Fair | Care needed | Avoid heat, steaming, chemicals and ultrasonic; may fade with time | ||
| FD/S | Dyed to improve appearance; dye may be selective in coverage | Common | Good to Fair | Care needed | Avoid heat, steaming, chemicals and ultrasonic; may fade with time | ||
| H/M | Heated to intensify brown/orange color | Common | Good | Care needed | Avoid heat, steaming, chemicals and ultrasonic | ||
| Jasper (see Quartz-Chalcedony) |
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| Kornerupine | 6.5-7 | N | None | - | - | Care needed | Brittle; handle with care |
| Kunzite (see Spodumene) |
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| Kyanite | 4-7 | N | None | - | - | Care needed | Somewhat brittle and softer in one direction; handle with care |
| Labradorite (see Feldspar) |
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| Lapis Lazuli | 5-6 | ||||||
| All varieties | FD/S | Dyed to improve appearance | Common | Fair | Care needed | Avoid heat, steaming, chemicals and ultrasonic; may fade with time | |
| F/M | Coated or impregnated with colorless filler to improve appearance and durability | Rare | Good to Fair | Care needed | Avoid heat, steaming, chemicals and ultrasonic | ||
| Larimar (see Pectolite) |
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| Malachite | 3.5-4.5 | F/M | Impregnated with colorless hardened or unhardened filler to improve appearance | Occasional | Good to Fair | Care needed | Avoid heat, steaming, chemicals and ultrasonic |
| Marcasite | 6-6.5 | N | None | - | - | Care needed | Brittle; handle with care |
| Maw-sit-sit | 6-8 | N | None | - | - | Care needed | Avoid heat, steaming, chemicals and ultrasonic |
| Moldavite (see Tektite) |
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| Montebrasite (see Amblygonite) |
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| Mookite (see Quartz-Chalcedony, Jasper) |
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| Moonstone (see Feldspar) |
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| Morganite (see Beryl) |
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| Mother-of-pearl (see Pearl) |
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| Nephrite Jade | 6-6.5 | ||||||
| All varieties | FD/S | Dyed to improve appearance; dye may be selective in coverage | Common | Good to Fair | Care needed | Avoid heat, steaming, chemicals and ultrasonic; may fade with time | |
| Cat's eye | N | None | - | - | Care needed | Avoid heat, steaming, chemicals and ultrasonic | |
| Obsidian | 5-6 | N | None | - | - | Care needed | Heat sensitive and brittle |
| Oligoclase (see Feldspar) |
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| Onyx (see Quartz-Chalcedony) |
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| Opal | 5.5-6.5 | ||||||
| All varieties except fire opal | F/S | Impregnated with colorless hardened or unhardened filler to improve appearance and/or durability | Occasional | Fair | Care needed | Avoid heat, steaming, chemicals and ultrasonic | |
| Matrix | FD/S | Dyed via sugar solution infilling, then acid bath to dye background and enhance color play and intensity | Common | Good | Care needed | Avoid heat, steaming, chemicals and ultrasonic | |
| Fire opal & moss opal | N | None | - | - | Care needed | Avoid heat, steaming, chemicals and ultrasonic | |
| Pearl, Natural and Cultured | 2.5-4.5 | ||||||
| All varieties, including mother-of-pearl | FD/L-S | Dyed to improve color. May include use of colored nuclei and/or heat | Common | Fair | Care needed | Avoid exposure to UV light, heat, steaming, chemicals and ultrasonic | |
| B/L | Bleached to improve color and appearance | Common | Good | Care needed | Avoid exposure to UV light, heat, steaming, chemicals and ultrasonic | ||
| C/M | Coated to improve appearance | Occasional | Fair | Care needed | Avoid exposure to UV light, heat, steaming, chemicals and ultrasonic | ||
| I/S | Irradiated to improve color | Occasional | Good | Care needed | Avoid exposure to UV light, heat, steaming, chemicals and ultrasonic | ||
| Pectolite (aka 'Larimar') | 4.5-5 | N | None | - | - | Care needed | Somewhat soft; handle with care |
| Peridot | 6.5-7 | N | None | - | - | Care needed | Avoid heat, steaming, chemicals and ultrasonic |
| All varieties | H/L | Heated to improve color | Occasional | Good | Care needed | Avoid heat, steaming, chemicals and ultrasonic | |
| F/L | Impregnated with colorless hardened or unhardened filler to improve appearance and/or durability | Occasional | Fair | Care needed | Avoid heat, steaming, chemicals and ultrasonic | ||
| Petalite | 6-6.5 | N | None | - | - | Care needed | Brittle; handle with care |
| Pezzottaite | 8 | F/L-S | Impregnated with colorless hardened or unhardened filler to improve appearance and/or durability | Occasional | Fair | Care needed | Avoid sudden temperature changes, heat, steaming, chemicals and ultrasonic |
| Phenakite | 7.5-8 | N | None | - | - | Care needed | Brittle; handle with care |
| Prehnite | 6-6.5 | N | None | - | - | Care needed | Brittle; handle with care |
| Pyrite | 6-6.5 | N | None | - | - | Care needed | Brittle and heat sensitive; handle with care |
| Quartz | 7 | ||||||
| Cat's eye, rutilated, tourmalinated, rose, rock crystal | N | None | - | - | Normal | - | |
| Amethyst | H/L | Heated to improve color | Occasional | Good | Care needed | Whether treated or not, may fade with prolonged exposure to light or heat | |
| Ametrine, translucent blue (aka 'blue moon'), green (aka 'prase' or 'prasiolite') | H/L | Heated to improve color | Common | Good | Care needed | Whether treated or not, may fade with prolonged exposure to light or heat | |
| Citrine | H/S | Produced by heating various types of quartz | Common | Good | Care needed | Whether treated or not, may fade with prolonged exposure to light or heat | |
| Amethyst, green (aka 'prase' or 'prasiolite'), lemon quartz, smoky quartz, blueberry quartz | I/M | Irradiated to improve color | Common | Fair | Care needed | May fade in light or heat; avoid heat, steaming, chemicals and ultrasonic | |
| Quartz-Chalcedony (aka 'Cryptocrystalline' Quartz) | 6.5-7 | ||||||
| Agate, banded, blue, green, jasper | FD/S | Dyed to improve appearance | Common | Good to Fair | Care needed | May fade in light or heat; avoid heat, steaming, chemicals and ultrasonic | |
| Black (onyx) | H/S | Impregnated/acid treated to alter color | Always | Good | Care needed | May fade in light or heat; avoid heat, steaming, chemicals and ultrasonic | |
| Carnelian, sard; sardonyx | FD/S | Dyed to improve appearance | Occasional | Good to Fair | Care needed | May fade in light or heat; avoid heat, steaming, chemicals and ultrasonic | |
| H/M | Heated to improve appearance | Common | Good | Normal | - | ||
| Chrysoprase, bloodstone | N | - | - | - | Normal | - | |
| Quartzite & Microcrystalline Quartz | 6.5-7 | ||||||
| Aventurine | FD/S | Dyed to improve color | Common | Fair | Care needed | Dye may fade; avoid heat, steaming, chemicals and ultrasonic | |
| Black | I/M | Irradiated to improve color | Common | Good | Care needed | May fade in light or heat; avoid heat, steaming, chemicals and ultrasonic | |
| Other quartzite | FD/S | Dyed to improve or completely change color | Common | Fair | Care needed | Dye may fade; avoid heat, steaming, chemicals and ultrasonic | |
| Tiger's eye | H/L | Heated to improve color | Common | Good | Normal | - | |
| B/L | Bleached to improve color | Common | Good | Normal | - | ||
| FD/S | Dyed to improve or completely change color | Common | Fair | Care needed | Dye may fade; avoid heat, steaming, chemicals and ultrasonic | ||
| Rhodonite | 5.5-6.5 | ||||||
| All varieties | FD/S | Dyed to produce various colors | Common | Fair | Care needed | Dye may fade; avoid heat, steaming, chemicals and ultrasonic | |
| Ruby (see Corundum) |
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| Sapphire (see Corundum) |
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| Sard (see Quartz-Chalcedony) |
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| Scapolite | 6 | N | None | - | - | Care needed | Brittle; handle with care; yellow gems may fade in light or heat |
| Serpentine | 4-6 | ||||||
| All varieties | F/M | Impregnated with colorless filler to improve appearance | Common | Good to Fair | Care needed | Avoid heat, steaming, chemicals and ultrasonic | |
| FD/S | Dyed to alter color | Rare | Fair | Care needed | Dye may fade; avoid heat, steaming, chemicals and ultrasonic | ||
| Shell | 4 | ||||||
| Pink | FD/S | Dyed to improve color | Common | Fair | Care needed | Dye may fade; avoid heat, steaming, chemicals and ultrasonic | |
| Sillimanite (Fibrolite) | 6--7 | N | None | - | - | Care needed | Brittle; handle with care |
| Sodalite | 5.5-6 | FD | Dyed to improve color | Rare | Fair | Care needed | Dye may fade; avoid heat, steaming, chemicals and ultrasonic |
| Spectrolite (see Feldspar-Labradorite) |
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| Sphene | 5-5.5 | N | None | - | - | Care needed | Soft and brittle; handle with care; avoid heat, steaming, chemicals and ultrasonic |
| Spinel | 7.5-8 | ||||||
| All varieties | F/L-M | Impregnated with colorless filler to improve appearance | Rare | Fair | Care needed | Avoid heat, steaming, chemicals and ultrasonic | |
| Spodumene | 6.5-7.5 | ||||||
| Kunzite | H/L | Heated to improve color | Common | Fair | Care needed | Natural and/or treated material may fade; avoid heat, strong light, ultrasonic | |
| I/M | Irradiated and heated to improve color | Common | Fair | Care needed | Natural and/or treated material may fade; avoid heat, strong light, ultrasonic | ||
| Green (aka 'hiddenite') and yellow | I/S | Irradiated to produce green color | Rare | Poor | Special caution | Color fades in light or heat | |
| Sugilite | 6-6.5 | N | - | - | - | Care needed | Avoid heat, steaming, chemicals and ultrasonic |
| Sunstone (see Feldspar) |
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| Tanolite (see Iolite) |
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| Tanzanite (see Zoisite) |
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| Tektite | 5.5-6.5 | ||||||
| Brown, green (aka 'moldavite') | N | None | - | - | Care needed | Brittle; handle with care | |
| Topaz | 8 | Care needed | Somewhat brittle; handle with care | ||||
| Blue | HI/S | Irradiated to a brown color, followed by heating to blue | Common | Good | Care needed | If neutron irradiated to produce blue color, refer to NRC for safety requirements; somewhat brittle; handle with care | |
| Brown, yellow, orange | H/L | Heated to improve color | Common | Good | Care needed | Somewhat brittle; handle with care | |
| Pink, red, orange | I/M | Irradiated to improve color | Occasional | Poor | Special caution | Color fades in light or heat; somewhat brittle; handle with care | |
| All colors | C/S | Coated in various colors | Common | Fair | Care needed | Avoid repolishing, which removes coating; some coatings also damaged by chemicals and ultrasonic; somewhat brittle; handle with care | |
| Tourmaline | 7-7.5 | ||||||
| Various colors | H/L | Heated to improve color | Common | Good | Care needed | Avoid heat, steaming, chemicals and ultrasonic | |
| I/L-M | Irradiated to improve color | Common | Good | Care needed | Avoid heat, steaming, chemicals and ultrasonic | ||
| F/L-M | Impregnated with colorless filler to improve appearance | Occasional | Fair | Care needed | Avoid heat, steaming, chemicals and ultrasonic | ||
| FD/S | Dyed to improve color | Rare | Fair | Care needed | May fade in light or heat; avoid heat, steaming, chemicals and ultrasonic | ||
| Turquoise | 5-6 | ||||||
| All varieties | F + I/S | Impregnated with colorless filler to improve appearance and durability; irradiation may be used to harden filler | Common | Good to Fair | Care needed | Avoid heat, steaming, chemicals and ultrasonic | |
| FD/S | Dyed to improve color | Rare | Fair | Care needed | Avoid heat, steaming, chemicals and ultrasonic | ||
| Vesuvianite (aka Idocrase) |
6-7 | N | None | - | - | Normal | - |
| Zircon | 6.5-7.5 | ||||||
| Blue, yellow, orange, green, colorless | H/L-S | Heated to improve color | Common | Fair | Care needed | Color may fade with time; can be restored by reheating | |
| Zoisite | 6-7 | ||||||
| Tanzanite, green tanzanite & chameleon tanzanite | H/L-S | Heated to improve color | Common | Good | Care needed | Avoid sudden temperature changes, heat, steaming, chemicals and ultrasonic | |
| Tanzanite | C/S | Coated to improve color | Rare | Fair | Care needed | Avoid repolishing, which removes coating; some coatings also damaged by chemicals and ultrasonic | |
| Zultanite (see Diaspore) |
Gem Enhancement & Care Chart-Other Gems
Gemstone |
Hardness |
Code & Degree |
Enhancement Method |
Frequency Used |
Stability |
Care Required |
Special Advice |
|---|---|---|---|---|---|---|---|
| Anatase | 5.5-6 | N | None | - | - | Care needed | Avoid chemicals and ultrasonic |
| Anglesite | 2.5-3 | N | None | - | - | Care needed | Avoid chemicals and ultrasonic; brittle and soft; avoid thermal and physical shock |
| Apophyllite | 4.5-5 | N | None | - | - | Care needed | Avoid chemicals and ultrasonic; brittle and soft; avoid thermal and physical shock |
| Aragonite | 3.5-4 | N | |||||
| Axinite | 6-7 | N | None | - | - | Care needed | Brittle; avoid shock |
| Barite | 2.5-3.5 | N | None | - | - | Care needed | Fragile; handle with care |
| Bastnäsite | 4-4.5 | N | None | - | - | Care needed | Fragile; handle with care |
| Boracite | 7-7.5 | N | None | - | - | Normal | - |
| Burbankite | 3.5-4 | N | None | - | - | Care needed | Fragile; handle with care |
| Bustamite | 5.5-6.5 | N | None | - | - | Care needed | Fragile; handle with care |
| Calcite | 3 | N | None | - | - | Care needed | Fragile; handle with care |
| Cassiterite | 6-7 | N | None | - | - | Care needed | Brittle; handle with care |
| Celestite | 3-3.5 | N | None | - | - | Care needed | Fragile; handle with care |
| Cinnabar | 2-2.5 | N | None | - | - | Care needed | Fragile; handle with care |
| Creedite | 4 | N | None | - | - | Care needed | Fragile; handle with care |
| Datolite | 5-5.5 | N | None | - | - | Care needed | Somewhat fragile; handle with care |
| Dolomite | 3.5-4 | N | None | - | - | Care needed | Fragile; handle with care |
| Dumortierite | 7-8.5 | N | None | - | - | Normal | - |
| Ekanite | 5-6.5 | N | None | - | - | Special caution | May be radioactive; should not be worn in jewellery or kept near skin |
| Eosphorite | 5 | N | None | - | - | Care needed | Somewhat soft; handle with care |
| Euclase | 7.5 | N | None | - | - | Care needed | Brittle; avoid heat, steaming, chemicals and ultrasonic |
| Eudialyte | 5-5.5 | N | None | - | - | Care needed | Somewhat soft; handle with care |
| Genthelvite | 6-6.5 | N | None | - | - | Normal | - |
| Haüyne | 5.5-6 | N | None | - | - | Care needed | Fragile; handle with care |
| Hemimorphite | 5 | N | None | - | - | Care needed | Somewhat soft; handle with care |
| Herderite | 5-5.5 | N | None | - | - | Care needed | Somewhat soft; handle with care |
| Howlite | 3-3.5 | ||||||
| Blue | FD/S | Dyed to improve color | Always | Good to Fair | Care needed | Avoid heat, steaming, chemicals and ultrasonic; may fade over time; Somewhat soft; handle with care | |
| White | N | None | - | - | Care needed | Somewhat soft; handle with care | |
| Leifite | 6 | N | None | - | - | Care needed | Brittle; handle with care |
| Leucite | 5.5-6 | N | None | - | - | Care needed | Brittle; handle with care |
| Manganotantalite | 5.5-6.5 | N | None | - | - | Care needed | Somewhat brittle; handle with care |
| Mellite | 2-2.5 | N | None | - | - | Care needed | Soft and brittle; handle with care; avoid heat, steaming, chemicals and ultrasonic |
| Milarite | 5.5-6 | N | None | - | - | Care needed | Brittle; handle with care |
| Monazite | 5-5.5 | N | None | - | - | Special caution | May be radioactive; should not be worn in jewellery or kept near skin |
| Natrolite | 5-5.5 | N | None | - | - | Care needed | Soft and brittle; handle with care; avoid heat, steaming, chemicals and ultrasonic |
| Nuumit (Nuumite) | 5-6 | N | None | - | - | Normal | - |
| Painite | 8 | N | None | - | - | Normal | - |
| Parisite | 4.5 | N | None | - | - | Care needed | Soft and brittle; handle with care; avoid heat, steaming, chemicals and ultrasonic |
| Pollucite | 6.5-7 | N | None | - | - | Care needed | Brittle; handle with care |
| Poudretteite | 5 | N | None | - | - | Care needed | Somewhat soft; handle with care |
| Pyroxmangite | 5.5-6 | N | None | - | - | Care needed | Brittle; handle with care |
| Remondite | 3-3.5 | N | None | - | - | Care needed | Soft and brittle; handle with care; avoid heat, steaming, chemicals and ultrasonic |
| Rhodochrosite | 3.5-4 | N | None | - | - | Care needed | Soft and brittle; handle with care; avoid heat, steaming, chemicals and ultrasonic |
| Rhodonite | 5.5-6.5 | ||||||
| All varieties | FD/S | Dyed to produce various colors | Common | Fair | Care needed | Dye may fade; avoid heat, steaming, chemicals and ultrasonic | |
| Rutile | 6-6.5 | N | None | - | - | Care needed | Brittle; handle with care |
| Scheelite | 4.5-5 | N | None | - | - | Care needed | Soft and brittle; handle with care; avoid heat, steaming, chemicals and ultrasonic |
| Scolecite | 5-5.5 | N | None | - | - | Care needed | Soft and brittle; handle with care; avoid heat, steaming, chemicals and ultrasonic |
| Sellaite | 5-5.5 | N | None | - | - | Care needed | Brittle; handle with care |
| Senarmontite | 2-2.5 | N | None | - | - | Care needed | Soft and brittle; handle with care; avoid heat, steaming, chemicals and ultrasonic |
| Serandite | 4.5-5 | N | None | - | - | Care needed | Soft and brittle; handle with care; avoid heat, steaming, chemicals and ultrasonic |
| Shortite | 3 | N | None | - | - | Care needed | Soft and brittle; handle with care; avoid heat, steaming, chemicals and ultrasonic |
| Siderite | 4 | N | None | - | - | Care needed | |
| Sinhalite | 6.5-7 | N | None | - | - | Normal | - |
| Smithsonite | 4-5 | N | None | - | - | Care needed | Soft and brittle; handle with care; avoid heat, steaming, chemicals and ultrasonic |
| Sphalerite | 3.5-4 | N | None | - | - | Care needed | Soft and brittle; handle with care; avoid heat, steaming, chemicals and ultrasonic |
| Staurolite | 7-7.5 | N | N | - | - | Care needed | Brittle; handle with care |
| Thaumasite | 3.5 | N | None | - | - | Care needed | Brittle; handle with care |
| Thomsonite | 5-5.5 | N | None | - | - | Care needed | Soft and brittle; handle with care; avoid heat, steaming, chemicals and ultrasonic |
| Titanium | 7 | ||||||
| Druzy | C/S | Coated to produce rainbow effect | Common | Good | Normal | - | |
| Tremolite | 5-6 | N | None | - | - | Care needed | Brittle; handle with care |
| Unakite | 6-7 | N | None | - | - | Normal | - |
| Villiaumite | 2-2.5 | N | None | - | - | Care needed | Soft and brittle; handle with care; avoid heat, steaming, chemicals and ultrasonic |
| Willemite | 5.5 | ||||||
| Blue | H/S | Heated to change color from white to blue | Rare | Unknown | Care needed | Brittle; handle with care | |
| Wilsonite | 3-4 | N | None | - | - | Care needed | Soft and brittle; handle with care; avoid heat, steaming, chemicals and ultrasonic |
| Wulfenite | 2.5-3 | N | None | - | - | Care needed | Soft and brittle; handle with care; avoid heat, steaming, chemicals and ultrasonic |
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