Irradiating a stone does not change its composition, and therefore, does not change the stone's inherent healing properties. Changing the stone's color, however, does have an effect on healing properties when it is used for color therapy, since color healing is not dependent upon what composition the stone has, but rather on what color the stone is.
Amethyst can be irradiated to resemble many other types of quartz, such as citrine, prasiolite, or smoky quartz. The color the amethyst turns depends upon which mine it is from.
So let's take, for example, an amethyst which has been irradiated to a deep golden or yellowy-orange color to resemble citrine. The stone's healing properties will not become those of citrine just because it now looks like citrine. Irradiating a stone does not chemically (or magically) change a stone into a different stone. It merely alters its color.
And so, compositionally, the stone is still an amethyst and will retain the healing properties of an amethyst. But, the amethyst is no longer purple, and so it will no longer have the healing abilities associated with the color purple. Instead, it will have the color healing properties associated with the color yellow.
Heat treatment, or annealing, uses heat and a combination of chemicals, such as beryllium, borax, lead, and tantalum, to permanently lighten, darken, or alter a stone's color to make it more visually appealing. Heat treatment does not affect a stone's healing properties unless it changes its color, in which case, only its usage in color therapy will change.
Many gemstones, such as aquamarine, ruby, topaz, sapphire, fluorite, ametrine, citrine, tanzanite, amethyst, morganite, tourmaline, amber, and zircon, are commonly heat-treated.
There are many other enhancement methods that use heat to enhance a stone, one of which is filling. Filling uses heat and borax or other fluxes and solvents to fill cracks and cavities in the surface of the stone with compounds such as lead glass, resin, or plastic. Filling improves the look of a stone and enhances its color, but it does not change its healing capabilities.
Commonly filled stones include: emerald, opal, ruby and sapphire.
Vapor deposition is another type of enhancement that uses extreme heat. Vapor deposition is the depositing of an element onto a stone or crystal through the use of heat and chemicals that bond the element to the crystal's lattice structure.
Aura crystals, such as aqua aura, flame aura, and angel aura, are an example of crystals that have been enhanced (or even created, you could say) through vapor deposition. In this instance, the crystal's healing properties ARE affected because the element becomes a part of the stone's composition, thus essentially creating a whole new stone.
Aqua aura, for example, is clear quartz with vaporized gold bonded to it. The mating of clear quartz with gold gives aqua aura a combination of its own unique healing properties derived from those of both quartz and gold.
Impregnation is the filling in of cracks and crevices on the surface of a porous stone using a colorless compound such as oil, wax, or resin. Oiling and waxing are the two most common forms of impregnation.
While oiling and waxing are often used to improve a stone's clarity, luster, and overall appearance, they are also sometimes used to strengthen and stabilize the stone. Brittle stones, such as opal, are routinely oiled to make them less likely to chip or break.
Other commonly waxed or oiled stones include: amazonite, lapis, bixbite, jadeite, azurite, peridot, coral, malachite, emerald, and serpentine. Impregnation does not affect a stone's healing properties or potential.
Another common way to enhance a stone's appearance is to dye it. Sometimes the stone is dyed its natural color to deepen or to even out the individual stone's color. When a stone is dyed its natural color, the healing abilities of the stone are not affected in any way.
This is common of stones such as black onyx, lapis, turquoise, jadeite, tiger eye, rhodonite, coral, serpentine, aventurine, malachite, jasper, and amber.
Other times the stone is dyed in all sorts of fantastic colors to give the stone more visual appeal and interest. Agate, which is dyed in any color imaginable, is probably the most common stone to be dyed for this reason.
Another stone that is commonly dyed is howlite. Most often, it is dyed a turquoise color to make it resemble turquoise. Turquoise-dyed howlite is sometimes referred to as turquenite. Turquenite is a simulated stone, which is a stone that is made to look like another stone. In the case of turquenite, it may look like turquoise, but dying howlite a blue-green color does not magically turn it into turquoise, and so the stone will not have any of the healing properties associated with turquoise.
Simulants never have the same healing energies as the stone they mimic because the simulant stone is a different stone entirely with a completely different chemical composition from the stone it is made to look like. The only healing use for a simulated stone is in color therapy.
When a stone is dyed an entirely different color from its natural color, the stone retains its regular inherent healing abilities, but also takes on the healing properties associated with its new color. Turquenite, therefore, has the healing abilities of howlite and the color turquoise.
So, in general, lab-enhanced stones are still effective healers. Lab enhancements do not remove or reduce a stone's healing potential. Most enhancements (other than vapor deposition) do not affect a stone's healing properties, unless the enhancement has changed the stone's color, in which case, only the stone's color-healing properties change. The properties inherent in the stone's composition remain the same.
Polished or rough: which is better?
The answer to this question really boils down to personal preference: which you are more attracted to and which you like working with better.
Stones can be cut, polished, tumbled, faceted, shaped, or left in a rough, or natural, state. All forms of stone are suitable for use in healing. No matter whether it is rough or smooth, and regardless of the stone's shape or cut, the stone will always retain its same healing abilities and effectiveness.
Some like the natural feel and look of rough stones, which can make one feel closer to the earth and more grounded. And some prefer the smoothness of a polished stone, which can have a soothing effect when rubbed on the body, or held in the hand. And still others prefer to use both polished stones and rough stones depending on where they are using them and what they are using them for.
For example, when working outdoors, some may prefer to use rough stones to feel in harmony with Nature. But when carrying stones in a pocket, purse, or pouch, they may prefer to use tumbled stones or palm stones, as they are easy to carry and transport.
When doing body healing and massage, in which the stones are placed directly on the body, many prefer to use smooth or tumbled stones or massage wands as they are more comfortable feeling on the body compared to the rough texture and sharp edges that a stone in its natural state may have.
Don't worry about one shape or form being more or less effective than another because there isn't. And don't worry about which shape or form is more proper for the usage in which you intend to use it because none are. There is no right or wrong selection. Just go with what you like and what feels right for you.
Does size matter?
No, not really. Just as the shape of a stone does not affect its healing potential and effectiveness, size doesn't either. Once again, it is really a matter of personal preference.
Sometimes, one might choose a stone based on its size because one size may be more practical to use than another. For example, if you were going to be carrying a stone around in your pants pocket all day, you most likely would not want it to be a very large stone. A large stone might be awkward or difficult to carry, it would not leave any room for putting anything else in your pocket, and you might not want people to be wondering what the heck that strange bulge in your pants is. So, you may find it more practical to carry a small tumbled stone in your pocket. At that size, you could even carry several stones in your pocket!
An instance where you might wish to use a larger stone is when you will be using the stone for environmental healing. Depending upon which stone you use, an environmental healing stone can protect an area (such as a room) from negative or harmful energies, or it can remove them and/or transmute them into positive energies. Or it can improve the emotional atmosphere of a space by emitting peaceful, loving, or soothing energies. In any case, you may wish to use a larger stone for this as a larger stone will work more effectively and will work longer than a smaller stone would as it would not need to be cleansed as often. After all, the stone isn't there just to look pretty!