Type 1 Gemstones
The following gemstones are typically inclusion free:
All colors of Beryl (except Emerald and Red Beryl), Chrysoberyl (except Alexandrite) Kunzite, Quartz (smoky) Topaz, Green Tourmaline, Tanzanite, Zircon

VVS Minute to not detectable
VS Minor
SI1 Noticeable to obvious
SI2 Obvious to noticeable
I1 Prominent- moderate affect on appearance or durability
I2 Prominent - severe affect on appearance or durability
I3 Prominent- severe affect on beauty, transparency or durability

Type 2 Gemstones
Gemstones that normally may have a few inclusions:
Alexandrite, Andalusite, Chrome Diopsides, Iolite, Peridot, Quartz (Amethyst,Citrine,Ametrine) Rhodolite, Ruby, Sapphire, Spinel, Tourmaline, All Garnet and Tsavorite

VVS Minor
VS Noticeable to obvious
SI1 Noticeable to obvious (more obvious)
SI2 Obvious to prominent
I1 Prominent - moderate affect on appearance or durability
I2 Prominent - severe affect on appearance or durability
I3 Prominent - severe affect on beauty, transparency or durability

Type 3 Gemstones
Gemstones that normally do not come clean:
Emerald, Red Beryl, and Rubellite.

VVS Barely Noticeable
VS Noticeable to OBVIOUS
SI1 Obvious to prominent
SI2 Obvious to PROMINENT
I1 Prominent - considerable affect on appearance or durability
I2 Prominent - severe affect on transparency or durability
I3 Prominent - severe affect on beauty, transparency or durability