Clarity of Gemstones explained:

Natural gemstones vary by type of gem with the amount of inclusions naturally found.
All gems are listed with a clarity that will be at LEAST the clarity claimed or better. Many cases the gems clarity is better than listed, but as clarity can be subject to opinion, a safe estimate is made using a standard triplet 10x jewelers loupe under controlled lighting.

GIA Type 1 Clarity Chart- normally clean gems VVS Very Very Slightly Included - Minute to not detectable VS Very Slightly Included - minor, eye clean, only seen with 10x loupe SI1 Slightly Included - hard to see with the eye, seen under 10x loupe SI2 Slightly Included 2 - slightly obivious to the eye I1 Included 1 - visible inclusions but transparent I2 Included 2 - many visible inclusions that may affect transparency I3 Included 3 - prominent inclusions which effect transparency Type 1 Gemstones are gemstones that are normally found to be clean.  This includes gems such as Amethyst, Aquamarine, Blue Topaz, Citrine, Kunzite, Tanzanite, Yellow Beryl, Yellow Chrysoberyl, Diamond.

GIA Type 2 Clarity Chart- naturally included gems VVS Very Very Slightly Included - Minute to not detectable VS Very Slightly Included - eye clean, only seen with 10x loupe SI1 Slightly Included - noticable inclusions, several seen under 10x loupe SI2 Slightly Included 2 - slightly obivious to the eye I1 Included 1 - visible inclusions but mostly transparent I2 Included 2 - many visible inclusions that may affect transparency I3 Included 3 - prominent inclusions which effect transparency Type 2 Colored Gemstones by their nature have natural inclusions. (Inclusions are the norm) This includes gems such as Andalusite, Crysoberyl, Alexandrite, Corundum (i.e. Sapphire and Ruby), Garnet, Peridot, Quartz, Amethyst, Citrine, Ametrine, Spinel, Tourmaline, Zircon.

GIA Type 3 Clarity Chart- gems which are always included VVS Very Very Slightly Included - few inclusions seen with 10x loupe VS Very Slightly Included - mostly eye clean, only seen with 10x loupe SI1 Slightly Included - some seen inclusions with the eye, mostly seen with 10x loupe SI2 Slightly Included 2 - inclusions obivious to the eye I1 Included 1 - many visible inclusions I2 Included 2 - many visible inclusions that affect transparency I3/ Opaque Included 3 - not transparent by nature or from inclusions which may be large Type 3 Colored Gemstones by their nature have many natural inclusions. (Heavily Included is the norm) This includes gems such as Emerald, red Beryl, Rubellite Tourmaline. Precious Opal is naturally opaque for example and is always found this way.