Green gemstones seem, for some reason, to be both rarer and more expensive than stones of other colors. This holds particularly true for faceted gems. This list will give you an idea of some of the options out there.
Aventurine – A semitransparent, lightish green stone. A very attractive and reasonably priced material, aventurine is typically found in bead form.
Bloodstone – A dark, muddy green opaque stone with dark red patches. Available in bead form and occasionally as cabochons.
Chrome diopside - Another beautiful green emerald alternative and my stone of choice for emerald green. It is not cheap by any means, but far more affordable than emerald and does not require the unstable fracture filling treatments that are applied to most emeralds. Chrome diopside is sometimes referred to as Russian emerald due to its Siberian origins. Most commonly available as faceted gems.
Chrysoprase: A beautiful, semitranslucent apple green stone. Crysoprase is expensive, particularly clean crysoprase with good color and few inclusions…but it’s worth it. Normally sold as beads, cabochons, and very rarely faceted gems.
Emerald - The royalty of green gemstones. Emeralds are beautiful, but fraught with problems for the buyer who doesn’t have many thousands of dollars to spend. Emeralds rarely occur as beautifully colored, clear stones. Most of them have significant inclusions, color problems, and microfractures. Undisclosed oiling and epoxy filling to improve the appearance of a stone with tiny fractures is rampant at the highest levels of the trade. Emeralds are fragile and easily cracked. A decent tiny emerald can be had at a cost accessible to ordinary mortals, but a quality stone of any size will cost a great deal very quickly. This article discusses emerald treatments and care warnings.
I also have my doubts about the social responsibility of buying emeralds; major sources are Myanmar (Burma) and Columbia. This article in Professional Jeweler Magazine casually brings to light the violence surrounding a Columbian emerald mining operation. There are many beautiful alternatives to emerald, and I while I do use emeralds on occasion, I have to say I prefer some of the other options.
Green tourmaline: Green form of tourmaline. Gem grade, which is usually only found in faceted gem form, can be incredibly beautiful and comes in a wide range of shades. It is also available in cabs and beads which tend to have poorer, more muddy color.
Malachite: Opaque forest green stone with lighter green banding. Very beautiful. Available as cabochons and beads.
Maw maw sit sit
Tsavorite garnet – This beautiful, clear green stone is an excellent emerald alternative. Although in many cases the cost may be nearly as high as emerald, the clarity tends to be better and it is not as fragile.