Following is the list of the abbreviations we use for "Enhancement" that appear in the details section for each Gemstone we offer:

A (None)	Indicates either a gemstone that is not currently known to be enhanced or one that is so rarely enhanced that to give it an "E" symbol would mislead the public. Example: Amethyst is rarely known to be treated.
H	Indicates the stone has been heated to effect desired alteration of color, clarity, and/or phenomena. Example: Sapphire is commonly enhanced in this manner. Example: Citrine is commonly enhanced in this manner.
N	Indicates this particular gemstone has received no enhancement and the seller will guarantee this.
R	Indicates the gemstone has undergone Irradiation. This is the use of neutron or a combination of neutron with any other bombardment to alter a gemstone's color. May be followed by a heating process ("H"). Example: Blue Topaz is commonly enhanced in this manner.

Also see Gemstones Clarity Grades Explained .