Opaque: the gemstone will not transmit light through it.

Translucent, or cloudy: the gemstone transmits light, but you cannot see clearly through it.

Heavily Included: the gemstone is transparent, but the gemstone is littered with inclusions, which are very visible without magnification.

Moderately Included: the gemstone is transparent, but there are several inclusions, which are visible without magnification.

Slightly Included: the gemstone has some very minor inclusions, which may be visible without magnification.

Very Slightly Included (Eye-Clean): the gemstone has some very minor inclusions that are not readily visible without magnification. Some Inclusions may be visible without magnification once you see them under magnification and know exactly where to look.

Very Very Slightly Included: the gemstone has some very very minor inclusions which are difficult to see under magnification.

Loupe Clean (Clean): no inclusions were seen using 10x magnification. However the gemstone was not examined microscopically. The gemstone may be internally flawless or flawless.

Internally Flawless: the gemstone was examined under a microscope of at least 40x magnification, and no inclusions were seen. The gemstone has some external blemishes.

Flawless: the gemstone was examined under a microscope of at least 40x magnification and no inclusions were seen and the gemstone has no external blemishes.

The measure of visibility through a gemstone is known as its transparency. It is an often-overlooked characteristic when discussing gemstones of all varieties. Amethyst can sometimes be very lightly included, most commercial quality ranges from transparent to translucent.

Transparency is designated as follows: